A Tale of Two Siblings: Littermate Syndrome in Dogs


The idea of adopting littermate puppies can seem like an adorable, fun idea. They'll play with each other, keep each other company, and they're guaranteed to get along. Right? Unfortunately, not so much.

Let's talk about littermate syndrome and why bringing home littermates can be a recipe for disaster.

But for those of you who already have sibling pups at home, we'll also talk about proactive ways you can survive the growth and development of sibling puppies without sacrificing your sanity and the pups' well-being.

What is littermate syndrome, and why should I think twice about adopting littermate puppies?

  • Littermate syndrome is an anecdotal term that refers to a host of issues that tend to present when siblings are raised in the same household beyond the normal 8-10 weeks.
  • Littermate Syndrome Issue 1: Lack of Training and Socializing
    • Training, socializing, housetraining, and caring for two young puppies can be more difficult than you'd imagine. Often certain components of puppy rearing are lost or done halfheartedly when there's more than one pup, as so much time is dedicated to "surviving the madness."
  • Littermate Syndrome Issue 2: Hyperattachment
    • Littermate puppies can quickly become hyperattached, unable to cope without the presence of the other. Often one pup suffers with this more than the other. If this happens, you'll generally see frantic, panicked, fearful, or even aggressive behavior when the pups are separated.
  • Littermate Syndrome Issue 3: Inter-Dog Aggression 
    • Especially among same-sex siblings, fighting can become severe, even dangerous, as they reach maturity. Siblings often play hard, and fight harder.
    • Because many sibling pups are only socialized with each other, they may develop aggression or fear towards other dogs.

What if I've already brought home littermate puppies?

Don't panic! In many cases, littermates can grow up to lead normal, healthy lives in the same household.

Here's what you need to know:

  • Give the puppies periodic time apart every single day. That means they should be regularly walked separately, played with separately, and trained separately.
  • Do not allow the pups to share a crate.
  • Feed meals separately, and out of two separate bowls.
  • Remember that both dogs are individuals. They will have unique personalities, may be motivated differently, and may have different energy levels and quirks.
  • Bond with the puppies individually, so that they are able to focus on you and not solely with each other.
  • Socialize the puppies heavily between 8-16 weeks of age. They must meet people and other animals without their sibling present, and should be taken to novel locations separately. Worried about vaccines? Take a look at the American Veterinary Society of Animal Behavior's recommendations.

Need professional guidance on your littermate issues? We offer private and group online dog training that's accessible from anywhere in the world. More details here, or contact us.

108 thoughts on “A Tale of Two Siblings: Littermate Syndrome in Dogs

  1. I understand this article is a few months old now, but I am having very similar issues with two completely unrelated dogs, not even the same age or the same breed. Are there articles on non siblings behaving this way? One is a male Maremma Sheepdog named "Fionn", I've had him since he was 10 weeks old, he was 1 and 1/2 and very bonded to me and my older 4 yr old Aussie when I brought home an 8 week old male Australian Shepherd named "Bear". The minute I introduced Bear to Fionn, Bear ran right up to that 90 lb. dog and initiated play with him like he'd known him his whole life.

    I had to watch them as they were very rough with their play from day one and the size difference was concerning. They will tirelessly play at every opportunity, even now, ignoring both myself and the other Aussie on the farm. If I try to engage one, the other will wedge themselves into the situation (Playing fetch with Bear, Fionn will chase Bear and try to grab him while he's running back with the ball. If I try to pet Fionn, Bear will start mouthing Fionn's face and cheeks). They then engage in play with each other right away after they disrupted the activity. They behave this way towards the other Aussie as well, if she tries to play, they will intentionally exclude her. They are inseparable and now Bear is starting to teach Fionn (who is now over 2 years old, while Bear is 9 months) all kinds of bad habits. It is like they made their own separate mini pack and no one else is allowed to join.

    I can't call Bear unsocialized though. He loves meeting new people and dogs. I started obedience classes with him and he's doing great (aside from serious issues keeping his focus on me), but Fionn can't stand it. He loses it when I leave with Bear and any time I exit the gate with Bear for a training session where Fionn can't interfere. He huffs his cheeks, cries, whines, wails, even howls like he's in pain.

    Would building a kennel for Bear and only allowing supervised time out correct this obsession between them or should I seriously consider re-homing one before the problems get worse and possibly escalate into fighting?

    1. Oh man, I was hoping there was a reply to this. It's only been two months but has there been any progress?

      1. Hi I have never heard of littermate syndrome.i have two pug brothers from the same litter called Bill and Ben I got them at the age of 8 weeks there now nearly 14 years old and sadly bill will have to be sent over the rainbow bridge in the next 2 week due to a tumer in side his chest that nothing can be done for him so before he suffers really badly we know we cannot keep him and let him suffer I know Ben will be devasted when he's no longer around.i was looking for ways to help him when the time comes and to help my 6 year old frenchie.and I came across litter syndrome.my boys are very very close right from go they did everything together even the training walks and sleep together BUT from day one of me bringing home my 8 week old frenchi both bill and Ben have interacted with him they play with him he also sleeps with them sometimes in the middle of them.what I'm trying to say is my boys do not suffer with litter syndrome they love snuggling up on the sofa 1 with me 1 with the kids and buddy my frenchi snuggle up with who ever he wants to be with so litter syndrome dose not happen to all brother are sisters I don't know if its because there pugs so just love every one that they come in contact with.i need help in how do I cope and help my kids and the 2 other dogs to cope when bill has gone

        1. I am so sorry that you're going to have to say goodbye to your beloved pup! Dogs are incredibly resilient and generally recover well from the loss of a sibling. There are some really lovely books on pet loss that may help your kids – check out "The Invisible Leash." Thinking of you guys!

    2. Having two same sex dogs can lead to many fights as they compete for rank. Always best if having more than one to get opposite genders (however have to be careful if they are too young to be neutered/spayed)

      1. I had 2 female dogs, getting them one year apart. One passed at 13 years and the other at 14. Never had an issue with them.

    3. I would think this could clarify similar to littermate syndrome. The thing also to consider is that different dog breeds mature at different speeds. For example Labrador Retrievers don't typically reach adult status till 4-5 years old. Other dog breeds may take 1 and half years old to reach adult status. And then within this each dog is different as well maturing early or late. From the description you provided I would classify this as littermate syndrome from the actions going on. So I would follow the recommended treatment for the syndrome, most importantly "with BOTH dogs". I can understand wanting to treat the younger dog especially since that's when the problem started. But both dogs need to be recurving that same treatment and training separately and together. We adopted siblings, not know about littermate syndrome, but by happenstance I spent the majority of my time with one sibling and he with the other. Then brought them together usually at feedings and nights and playtime's. Training was done separately and together.
      When they were about 4-5 months old we took in a 12 week old Dachshund mix. We had never heard of littermate syndrome and immediately the new dog bonded with one of the older dogs. And they played and rough house and got along great. The first thing we started noticing was less then normal bonding with me or my husband. Then came the severe separation anxiety. Even to the point that if one of us left and the other stayed here he would moan and whine and cry the whole time. He has been all but untrainable except for sit when getting a treaty is involved. He hasn't really bonded with any of the other dogs or me and my husband. Here is a very lovable dog that always looks and acts sad. There are even times he will almost act like an abused dog; hunker down and freeze in place when he is told no or move. We previously had a Lhasa Also we adopted because it has what we now know to be littermate syndrome with it's sister. He was 7 when we adopted him and about a year later we adopted a 3 yo Labrador Retriever. The Lhasa was very aggressive towards other dogs and didn't know how to socialize with them. But with so work and dedication the two ended up becoming very close, even though there would still be random outbursts of aggression towards the much larger Lab. Luckily the Lab want aggressive back and allowed us to intervene for it's protection. We followed a lot of the same techniques when dealing with these two. I spent my time majorly with the Lab, my husband with the Lhasa, separately. And then they would come together a few times a day for walks and training was done both separately and together. We would usually always walk then at the same time but took them in different directions and courses. My current challenge is starting treatment for littermate syndrome in the younger Dachshund even though the other older dog does exhibit really any signs of having littermate syndrome. I hope this helps and kinda clarifies a multitude of things related to littermate syndrome and the various ways it can present and how we accidently avoided it/prevented without even knowing about it.

    4. Littermate syndrome is kind of a misnomer. This can happen to any two young, near in age, or new dogs brought into the household at the same time, not just "littermates"
      It is named as such, however, because that is the scenario most common when people are bringing two new young dogs home- that they are siblings/ littermates

    5. This sounds like the dogs are trying to heard each other, my friend with similar dogs as yours had the same issues. She had to just make sure to separate them while playing, they just get too rowdy and nip at heels and faces. I would seek out a behavior specialist to get advice. This can be super hard to train out considering the breeds, it’s just in their natures.

  2. I began to notice this. I now feed separately. They spend at least 3-4 hours a day kenneled seperately, nor even next to each other. We also take them out seperately. I do not want to re-home either but do notice the aggressive behavior between them Occassionally. Do I separate & put them in their kennels or let them fight it out?

    1. We have two goldendoodle sisters that are just past the 6 months age mark, they sleep separately at night and do like having alone time from each other throughout the day, but we do notice the aggression towards each other. What we do is separate them so that we assert our dominance, giving them almost a time out so they can calm down. But then we let them fight again so that they will be able to learn when too much is too much by when we separate them or let them fight. And if you are worried about them getting too rough with each other, we always have two toys handy to give to each of the puppies to distract them.

      1. I just spent $$$$ on my 11 mo old dobies they snapped yesterday 10 min full out fighting nothing I could do would stop it,lucky they are alive
        My trainer has had me read them in separate kennels separate dog runs and only get together occasionally although they see each other day in and day out the trainer wants to continually work with them can you really fix littermate syndrome or do I just keep spending thousands trying they both want to be alpha,I have worked with a trainer one training on the left one training on the right but Have never been together. I feel like eight months of training the future doesn’t look very bright to have them both walk beside me does anybody overcomes littermate syndrome.

  3. My littermate males are 3 years old. They are two of my pack of 7, so they have plenty of interaction with other dogs. They do sleep in separate crates now, after about 12 weeks old. Their own personalities have developed nicely, Dale is more loving and clingy to me, while Chip is more independent. I guess mine were easy as littermates because there was a larger pack.

    1. We just took in 2 female pups who are 2 out of our 6 I'm really hoping all works out like it did you for as we go everywhere & socialize as much as possible

      1. I have 2 Pointerdor pups 9 months old and I don't have any problems with them. I do separate them for walks and training sessions but I also do it together sometimes. They play rough too. There are times they seprate on their own. One pup loves to be outside and the other pup prefers to stay inside. I respect their difereances treat them accordingly.

      2. Hi Tony, Hope you get this message. I just adopted two girls from the same litter. I am having a tough time with them. They fight play where it is scary. How are you doing with your two girls. Thank you, Barbara

      3. I have 2 Alusky same litter sisters. They're going on 4 years old. At 18 months old they developed a vicious aggression towards one another. No matter what I tried it only got worse. For almost 2 1/2 years I've lived with gates throughout my house to keep them separated. I will NEVER choose between them so this is the life we live.

        1. We have 2 french bulldogs brothers, 1 yr old. They’ve always played rough but just started getting very aggressive with each other. They don’t mess with the Aussies, but they attack each other often over toys, us, or thinking they are going to get a treat. It’s been crazy.

          1. This is definitely a challenging age for male litermates, as both dogs are reaching sexual maturity. If not neutered already, this is something I'd strongly suggest talking to your vet about!

  4. I love how they say socially between 8 to 16 weeks but all vers and animal facilities won't let you in under about 20 weeks to socialize. I'm not sure what the professionals think we should do we can't just NOT socialize a puppy until it's 20 weeks. But everyone shines on you suggested it.

    1. Rachel, in answer to your comment, before they are fully vaccinated, puppies can be carried when they are out and about, so they can be introduced to the world via sight, sound, smell, and touch in some cases. They can watch other dogs, people and children. If you have friends with vaccinated, friendly dogs, then they can meet them. You can have a puppy on your knee and the dog can be brought in on a lead and allowed to sniff the puppy, etc. Once the vaccinations are in place, you can start to take them to environments which enable calm introductions to other pups and dogs, and also watching them from a safe distance. The ideal is to meet other pups and dogs one to one, so they don't get too hyper. Near my home there is a large park with grass, plants, river, lake, etc., and owners of small dogs and puppies often walk them there during times when children are in school. That sort of place is an ideal environment for a puppy to explore; see pushchairs, prams, toddlers, and generally grow in confidence.

    2. They won’t let you in that young to socialize because the puppy at that age would not have had all of his or her vaccines by then. It’s medically dangerous to socialize dogs in any surroundings when one could be a carrier of something serious and a puppy hasn’t been guarded against it yet. So to err on the safe side to keep a pup from getting an incurable death sentence, play time has to wait.

      1. I agree Kaitlyn puppies dont need to socialize until ti has all its needles while you waite for this you can get them used to you and there surroundings, their new home

  5. My litter mates are 14 years old, one male and one female . They have totally different personalities and needs. One is very outgoing and energetic while the other has always been somewhat neurotic. We have done most of what is in the list, more by instinct than any knowledge. Today is the first time I’ve ever heard of litter mate syndrome.

  6. My dogs are two year old pitbulls both very strong personalitys and from the same litter 2 weeks ago I noticed that they've been fighting and last night and this morning they literally tried to kill each other what do I do? Give the one away or put one down I need advice asap as I love both my dogs and am scared they might kill each other

  7. My partner and I were unaware of this issue until it was too late and the dogs began fighting. We now have them seperate nearly all the time out of fear that they will keep fighting and cause each other serious damage. We have a little one on the way and are looking at moving for work I doubt we will be able to keep them separate like we have been. What can we do now to reintegrate them to being together more often? I’m not willing to rehome them they are apart of our family and I’ll do what I have to to make it work.

    1. I have a vet friend who raised two males from a Giant Schnauzer together, not knowing this either. They need to always have one crated or there is serious damage. She once asked me to come into the clinic with her so she could sew up Thunders’ leg, as he would have bitten anyone else. Vets do not have enough regular training in school on raising healthy puppies
      to advice clients on behavior.

  8. I had two littermate lab sisters – completely diffrent personalties – loved each other deeply and very loyal to one another but never any glaring issues. When puppies it was impossible to train them when together – they would make eye contact and off they were. so I separated, walked separate and one-on-one time with both. I did this more out of sanity since I saw that training them together wasn't possible. Once they reached maturity and trained – all was well. I never heard of littermate syndrome until recently.

    1. Hi Kathy, we have two Labrador girl litter mates and they are two years of age now. Luckily they don’t fight but we have problems with them pulling on lead. Was wondering if I could chat to you to get advice on this please ?


      1. I saw this and wanted to let you know that we found special harness that attaches st thd front. It prevents all pulling. Walks are enjoyable now! I have also noticed that they have stopped pulling on the regular leads now ad well. Hit the pet store!

  9. I have 2 female littermates (about a yr n a half old), they're german shepherds. I've basically done everything it says about raising littermates. However, both of the girls came in heat at basically the same time. I had my partner bring our male down to breed them (one of the sisters belongs to him). Even tho I put him with each girl separately, switching from one to another, and I never saw him tied with either, only one got pregnant. Unfortunately not my girl and I don't understand why? Could anyone give me an answer? I've been thinking everything you can imagine. I was so looking forward to seeing the babies she would have, she's a black n tan except more like blonde n tan, the sire black. Will she get pregnant next time or…? Someone please give me an answer?

    1. Please don’t breed your dogs there are thousands of German shepherds in shelters that need homes or wil be put down
      Please be responsible
      Jeeze look at the dogs that will die because they have no homes
      Don’t contribute to the problem

  10. Everything mentioned here is true to the T! I have two litter mates (both boys) they will be 12 soon. But one is misses the other more but he’s also the independent one which is interesting. They do fight with each other when they see other dogs. Don’t socialize well with dogs unless the dogs are super easy going and around their size. Training them was so hard because when I thought I saw progress one would fall out of line. But all that I wouldn’t trait it for the world they are my everything!!!

  11. A few months ago we went to adopt a young husky puppy. I was to pick out the one i wanted. I chose a young female. Just when I thought we were leaving. My grandfather (I live with my grandparents) decided to suddenly get a second one. A male. At first we had no issues. They would cuddle and play with one another. They have always slept separately. Been walked separately. I try to train them separately but often fail too. One was going to puppy class, with the idea of taking the other one after the first one was done her lessons.
    Then this virus thing happened and I have not been able to get them to socialize at all with others. I have a hard time calming them if anyone in my family drops by for something. It has gotten to the point that they were suddenly start fighting when they get too overly excited.
    Ever since they turned four months old (they are five now). They been constantly wrestling like they would when we first got them. I always allowed it because I read it is good for puppy play. But lately it has gotten out of hand. If it goes too far it can lead to a fight.
    I been working to try and get them to stop. But I can't get their attention unless I use treats. My grandparents scold me for this saying they will fight just to get the treats. But I have tried everything. Clapping my hands. Ordering them by saying "Enough", a whistle, You name it.
    I can't just get in there and grab them because innocent play will suddenly become aggressive. My grandparents do that and it always leads to a fight.
    Any other time they cuddle with one another. Play with one another. They know basic commands like sit, wait and such. Only thing I have trouble with has been come, and heel and not getting them to immediately run out the front door or back door or jumping on other people which I am working on.
    I really do not want to get rid of any one of them. I love them both. I am hoping when they are fixed it might help a bit. But that won't be till June. My stress level is getting to me. I just want them to get along more like they used too up until last month.

    1. I'm so sorry you're in this position! It is normal for these behaviors to kick off as dogs begin to reach full maturity. Typically these issues are a combination of management and behavior modification, and the most intense fights we see are often sibling dogs. They play hard and they fight hard, and often one blends into the other. If we can be of assistance via online private instruction, please don't hesitate to reach out.

      1. Hi Alex, it sounds like you have a lot of experience with littermate Syndrome- are you a dog trainer? I never heard of it before and we had more than one dog at a time while growing up. I just got 2 o my own pups- who are both Morkie and are 9 month’s apart. One is a year and 9 months and the other is a year and 3 months old. I’m just starting to experience horrible littermate syndrome between the 2. I’d love to chat about it if you have a lot of experience with this. Please let me know!

    2. I have the exact same problem, 2 husky litter mates (opposite sexes), I can't seem to get them to calm down as I separate them to spend one on one time with them and it's really hard. When they're together it's also nearly impossible to get their attention. They both have somewhat learned basic commands but the male is really tone deaf with or without his sister regardless and socializing is a nightmare in quarantine. They're good pups and extreme aggression hasn't happened yet but I only just learned of this too and am trying my best to get them to grow into healthy well behaved dogs. Regardless, I hope you you've been able to make progress with them :') I also wanted to ask if you where to have any tips so far?

  12. I have a litter of Anatolian puppies there were 19 in the litter, all survived. Now they are 12 weeks old and 7 remain to be rehomed. I sold a male last weekend and after he left, all heck broke loose. I surmise they are fighting for pack dominance. One pup in particular did not want to back down from the other, and now the whole bunch of them gang up on this pup. He has been bloodied multiple times around his neck. As I do work, I have had to separate him from the pack of pups. It does look like there will be no way to put them back together. Even his mom is bearing down on him. Is he just too big for his britches and they all want to diminish him? He seems a very easygoing pup. It all started when the biggest pup was laying under my lawn chair, and the beat up pup approached to be petted. Attack mode went the underchair layer, and it was on.

  13. Hi- didn’t know any better until reading your information. Have two 6-month old golden doodle females in one crate & it’s been this way ever since they cane home at 8 weeks. Will suddenly separating them into 2 crates cause too much anxiety? Is there a best practice at trying to separate them at this point?

  14. Hit
    We have 2 large mixed breed 6 month old Sisters. We trained them to walk alone and separately when they were younger. Most of he time they are fine, they play a little rough at times. We are on the road in an RV, though it is close quarters, they are handling it well. The problem we are now having is sometimes on our walks they go CRAZY, serious pulling, jumping and wrestling, and as suddenly as it started it stops, light a switched is turned on and off.

  15. We have 2 Samoyed Sibling Bitches, they're 18 months old now and man have we been through and still enduring hell when it kicks off. It started at 12 months and the fights aren't for the fainthearted, we've had two lots of stitches and another wound which didn't quite need them. The one was Pack leader when we picked her up, even over her bigger brothers, we have a placid stud and she doesn't really boss him but she has ragged our Chihuahua on one occasion. We've disciplined her so many times and it's obvious she knows she's in trouble as soon as she's kicked off, but curing it is proving incredibly difficult!

  16. I had two daschunds – male & female. Unfortunately, we thought crating them together would keep each other company. They have slept together for 14 yrs. Our female died 4 months ago, and the male dog won't sleep alone. He carries on all night. We started giving him hemp oil – it helped him sleep for 2 weeks. Now he is back to crying, barking & wimpering. I'm deseperate – don't know what to do!

    1. I'm so sorry about the loss of your pup, Kathryn! You may considering letting your male sleep out of the crate – he likely just needs some company, and human company will do just fine!

    2. Put him in bed with you. He's got onset separation anxiety losing his partner. He need you
      He can't be stuck in a crate alone after years of sleeping with his lifelong buddy. You must know that. Sorry about your loss but jeez. I feel bad for your dog💔

  17. We just adopted two border collie sisters – they are two months old and their fighting that looks like play has escalated today to a point that scared me. I’m trying to house train them and it’s been difficult if I’m doing it alone. But separating them, walking them separately, separate toys, crates, will be our next step. It’s a challenge and I feel like a fool for agreeing to get both, simply because they were the last two in the litter.

    1. Hang in there and don't beat yourself up! It sounds like you're doing everything right, and periodic separation at this age is going to be critical. But if things continue to escalate, I strongly recommend enlisting a professional (look for CPDT or IAABC certification) to help. Happy to find a referral for you in your area!

    2. Alexa, I am in the same situation! We just got two cattle lab mixes this week. Both are girls and 3 months old. We went to adopt one but fell in love with both. We knew it would a lot of work but somehow it feels more daunting that I expected. it's even hard with two kids in the house. I have a 7 & 8 year old. I feel so guilty because I feel like I am not giving my kids my full attention because I am on the puppies schedule. The pups are fighting and training has been difficult too. My husband says this will pass. Then he sees me upset and tired so he says maybe we should take one back to the rescue. I feel awful to do that plus it will break my children's heart. I guess I am just overwhelmed at the moment. Oh and I go back to work next month so I am worried about leaving the pups alone. I feel so emotional about this. I have regret and I love my pups at the same time.

      1. I can't tell you what to do, but I can tell you that I'm sending lots of good thoughts your way! You have to do what's right for you and your family, and there's no judgment either way. It's extremely normal to feel overwhelmed, and I would recommend getting some professional guidance via private training to help you decide what the best next step is for you. Happy to provide a referral in your area!

      2. Not sure what you ended up doing but we also have two cattle dog mix pups. They are 13 months old. They have such different personalities and reasons why they get triggered into too aggressive fighting. Usually though it’s around food, treats or “the ball”. During fetch, when coming in the house, if Raven (the bigger one at 40 lbs) thinks I’ve given her ball to Checkers (30 lbs) she will attack her most viciously. I use avoidance to solve that problem. I.e. I bring in Checkers first and get her settled, then I bring in Raven and take the ball away. Then I give them both a treat and all is well. The other day though, they were out in the field and Checkers found a frozen mouse or a horse-poop-cycle and was happily digging it up when Raven decided that instead of playing the much coveted and obsessive fetch game, that she needed the same poopcycle and went after Checkers most ferociously and in either pulling her off or the entanglement Checkers got hurt and was limping for a few days. This just makes me resolve even further to try more of the suggestions from above. They have their own crates but usually sleep with us at night. Do we need to stop this? They behave really sweetly in bed and have different spots, Checkers vying for the spot under my armpit and Raven by my feet. When people say feed them separately do they mean at different times? Or just in different bowls or in different rooms? Surprisingly Checkers is the one that growls if she feels Raven is too close to the food bowl. But if a treat is involved like a chewy one that lasts longer, not a quick treat, then Raven is the one that can get more aggressive. We usually just supervise the treats and are successful in staving off the shenanigans. Surprisingly also they usually don’t get into trouble when it comes to toys, Of course Raven always wants the toy she doesn’t have but they don’t seem to fight over them in the same way. It’s hard to walk them separately as my husband is not always able to help for health reasons. When I walk them together they sometimes want to fight each other, but I keep treats handy for Checkers to distract her before it escalates and sweet talk her to paying attention to me and that does the trick…I.e. getting it before it escalates. Funnily Checkers is usually the instigator on leash. So in summary, keep trying different things. Eventually it can be solved. Try to get it before it escalates, see what the triggers are. But I don’t have all the answers and I’m still trying to figure it out.

  18. We’ve had two Rat Terrier x Chihuahuas for nine years(Cory and Cody)…My Sister in law adopted Cody, had us babysit him for a day and told us there was one more of the same liter at the shelter. We went and got the last puppy the next day(Cory). Two weeks after we took Cory home, she asked us if we wanted Cody so they could be together. We took them and training looked different for both. They have very different personalities. Cody clings to me and Cory clings to my wife. They do most activities together and we haven’t had major sibling problems. Cory is a typical Chihuahua…loud, mean and bossy. But he’s a terrier too, so he loves hunting. Cody acts like a BIG baby all the time. But his Chihuahua only comes out when it needs too. (When his brother gets on his nerves) They are both very sweet in their own way. But they also don’t necessarily need to be around each other. Every once in a blue moon they’ll have a disagreement that will scare us because it comes out of nowhere. But they get along. I have Cory laying on hip and Cody on either side as we speak…quiet and still. Good Luck!

  19. Hi. My brother and I (we live in the same house) adopted to rottweiler puppies named Bach and Beethoven (both male) and for the past few days, they looked like they were having fun playing together until recently they started to fight hard wherein both my brother and I got scared that one of them might get hurt. Bach is a very calm puppy but he's always hungry while Beethoven get jealous very easily and ALWAYS crave for attention. Since the beginning, they had different cages, toys, walk schedule etc but I don't know how to remedy the situation for them to get along. Do you guys have any advice on what we should do?

    1. Adorable names, first of all! How old are the puppies currently? Sometimes littermate play looks so intense, it can be mistaken for fighting. It's great that you're already getting them separate time!

  20. It is not always littermates! I have 4 Beagles, two of whom are littermates, 8 years old now and never an issue. The other two were found running together, no issue with them either, have had them 4 years now. My problem is with my two Coonhounds. The first was a rehome, about 5 years old. The Beagles were terrified of him, of his size mainly, so he had no one to play with. A year later decided to get another Coonhound from a shelter, he was around 2-3 years old. I knew he was intact, and had him neutered 2 weeks later, he ended up with 3 surgeries, and sepsis from that neuter. Finally able to bring him home, and he proceeded to grab a razor off the showere wall and eat it all, back to hospital for a scope to be passed and fish for all the razor blade pieces. Regular vet saw one week later for re check and found heartworms. So he hasbeen crated for 7 months, I didn't want the other dogs to excite him, so he and I lived in my bedroom all this time. I am much more mom to the two Coonies than the Beagles, so he finally got a clean bill of health just when Covid came to town. So all we had was each other for a very long time. Now a new problem, jealously, between them over me, more "arguments". I do know how to keep multiple dogs, but these two have me puzzled. All I do is spend my time with them seperately and together. Sometimes it seems as if the more they are together the better things are, but then sometimes not. It is exhausting and any suggestions anyone might have to end the "Walker Wars" would be more than welcome.

  21. Good info. Just brought home 2 doodles 8 weeks old. They are crated together right now. What age should I be seoerating them so they dont get anxious without each other.

      1. I have two female shitzu’s almost 2 years old they are literates . I also have a 17 year tweenie they had all been getting along fine with an occasional mild fight just the two girls. My daughter got a pit at Christmas and the fights between my shitzus are getting terrible it’s like they want to tear each other to shredded and would if I didn’t separate them and put them both in time out crates but it’s just getting worse the pit is only 4 months some times they gang up on him he called down scared , I’m not certain but I think my daughter may have to regime her pit bc the level of violence between my girls is awful I pull them apart have to hold one over my head while my other girl jumps , barks , bites to the point I’m shaking by time I get them in their crates and they will still be growling at each other. Is there anything other than than the pit or the maturity of my girls that could be causing this much violent behavior between them ?

        1. Hi Mary! This sounds like a very serious and potentially dangerous situation – for now I recommend keeping the Shih Tzus separated completely, and be sure to get your daughter's dog lots of positive experiences with friendly dogs so that she has good experiences with dogs – otherwise the situation could absolutely get worse with time. I also suggest finding a professional trainer in your area to help you – let me know if you need a referral!

    1. I adopted 2 golden/lab mix males at 8 weeks old. The first night they started sleeping in separate crates. They are now 9 months old and 90+ lbs (I am 105lbs so I knew training was going to be imperative from the start). We started training separately and going to daycare as soon as they were old enough and had all of their vaccines. It is expensive at first but I believe it was a good investment. The daycare they go to is run by the same trainers we go to as well. At daycare, they are will different groups of dogs so they are socialized with different dogs and they learn how to play correctly with each other (they still play rough but not as rough). They are walked separately as well. If I take on to the pet store, then I take the other one to the pet store that same day for the same time frame etc. They now sleep out of their crate in my room separately at night but have the option of going to their crate if they want. They are crated separately still at other times but if they are not playing and just napping, they each have their own favorite spot in the house away from each other. I think the constant "away from each other" structure has helped tremendously.

    2. How are you going with your 2 doodles? We are about to get 2 cavoodles, and after reading this thread I am worried whether we have made the right decision in getting 2?

  22. We are in our 70's in good health at present. We have a fenced-in backyard. Our last dog died two years ago, so, we have reserved two puppies. The first, a mini Labradoodle, will be ready to come home on Jan 9, the second from a different breeder, a mini Goldendoodle, was just born yesterday so will be ready to come home on Jan 28th. They of course are not littermates but are we asking for big trouble here since they are so close in age? We never considered or knew about Littermate Syndrome. I'm thinking we could pass on this litter and wait for another but since she is just a small-time breeder it may be a long time to wait. Thank you for your advice.

    1. I would strongly recommend one pup at a time! Pick one puppy out of the two litters you're reserved for, really put 100% into raising that puppy, and then consider adding another one your first pup is fully mature at 12-18 months of age. It will make the whole process more enjoyable for everyone!

  23. I have a slightly different situation. Three weeks ago I brought home a second dog, a 15-month old neutered male heeler mix, Bandit. The previous owner just didn’t have the knowledge, time, or space for a high-energy breed. I already had a spayed female pit mix, about 2-years old. They get along and play well, although it seems my female is trying to be dominant lately. Bandit has quickly picked up on life here at my home and he fits right in, has already learned at least a dozen new “tricks”, and has perfect recall. My question is this: the man who rehomed Bandit to me is asking me if I would also take Bandit’s sister (who has been with the owners brother for the last 4months) because I’ve done so well with Bandit. Would this be a recipe for disaster? Would it “undo” all of Bandit’s progress?

    1. I wouldn't recommend it! It sounds like you've just gotten Bandit settled in, and adding in a littermate to the home (especially with an unrelated female in the home) could undo a lot of your progress.

  24. So I did this all wrong. I got two Dobermans Goose and Maverick, who spent their whole lives together. They were brought home in the same bed they shared a cage they did everything together. They would fight but never so violently. Never really had a issue with them till recently. They both had been feeling sick goose was feeling worse then maverick so we took both to the vet. And out of nowhere goose started fighting with maverick and they fought. Today was the second time it happened. Goose isn’t letting maverick out of his sight. I don’t know what to do. I don’t want to re home one of them because they’re my boys. But I also don’t want one of them to get hurt either.

    1. How old are they currently? Are they intact or neutered? Also, sickness can definitely exacerbate these types of issues – keep them separated until both are healthy. IF you see ongoing issues, feel free to contact us and we can get you set up with some virtual training!

  25. It is quite hopeless to know that now. I have two brood sisters, 6 months old each, who eat and sleep separately, but walk together. During the past few weeks we have noticed their very hostile behavior towards other dogs and people. They had very few episodes of fights with each other, and usually have a very friendly relationship. What can I do?

    1. Be sure to talk to your vet about spays for both dogs – if you have heat cycles with two female littermates, you could be in for some major fighting. Try walking them separately for now – otherwise, they're going to teach each other some bad habits that will be harder to break later on. It sounds like they are doing well overall, though! Separate walks for now will be critical. You can also check out our online Flip the Switch class, which runs every other month, which focuses specifically on leash reactivity.

  26. Hi there, if I have added two male littermates into my family, with one 11 year old fixed male already in the house, is it advisable to neuter both siblings or not?
    We are crating them apart, will be training apart (have already been doing this in different rooms of the house but they’re only 10 weeks atm so training isn’t too long) feeding apart, and once they have had their second jabs and can go out for walks will be walked separately, we were thinking of alternating them on walks with our adult dog too.
    The main question we have is about neutering the both of them. Thank you.

    1. It sounds like you are doing an excellent job so far- well done! This will be a question for your vet, but from a behavior standpoint, we do recommend neutering both pups once they get a bit older (your vet will be able to make a recommendation based on your dogs' breed, size, health, etc.).

  27. Hi, we rescued 2 puppies (male and female) a week ago. The vet thinks they're about 3 months old and we think they are a mixed Spanish hunting breed -with some German short-haired pointer in there. We live in a 1 room house but with acres and acres of land. (We spend most of our days outside.) We are feeding them separately and attempting to spend time with each one-on-one. The separate sleeping is a bit of an issue, they currently sleep together on the couch. Do you still recommend getting 2 separate crates even though they'll be in the same room? In the summer it will be warm enough to sleep outside. Thanks, any advice appreciated!

    1. This is totally up to you and your long-term preferences! It's important that the dogs are able to be confined separately in case you need for them to be separated (for example, if one had a medical procedure done) but it's ok to let them sleep together most of the time. Just make sure you practice some separate confinement time!

  28. Hi Tony, Hope you get this message. I just adopted two girls from the same litter. I am having a tough time with them. They fight play where it is scary. How are you doing with your two girls. Thank you, Barbara

  29. We have two jack rats, brother and sister. They couldn’t be more different! Everything was fine till they got fixed at 4/5months . Then aggressive behavior started to come out, they don’t lay together and rarely play together. But they can’t stand to be separated! If one leaves the house the other cries. Of corse they encourage bad behavior in each other like barking or digging. I am great at stopping them, bc they see me as boss. My husband on the other hand they love but treat him like a lower class dog and it’s taken two years for him to learn it’s not ok. My biggest problem is bathroom in the HOUSE! They will go to mark over each other’s potty!! It’s in two spots of my home but I can’t stand it ! They are two years old!! While I wish they laid together and were sweet like our last dogs , I will accept that they won’t, but the potty in the house is the thing that’s driving me nuts .

  30. My girls are 18 weeks old. I brought them home almost two months ago. Had NO idea about littermate syndrome (the rescue just wanted to get rid of them, so they never mentioned it). Boy have I been worried ever since I hit the Search button!! I've taken as many precautions and steps as I can based on what I've read. I still have some unanswered questions and inevitable worry, so I'm looking for some advice (or reinforcement?).

    I had them in the same crate for the first week they were home, then I separated them into two crates. They didn't lose a wink of sleep over it. Slowly, I started moving the crates apart so that now they are as far away from each other (in the same room) as can be. As soon as I make room in another bedroom, I'm going to try moving one out of the room. They go in their crates when told and never ever try to resist. They love their crates and their own space!! They eat out of separate bowls, usually both in their crates. Sometimes, I feed one in her crate and take the other in the bathroom to eat (just to make sure they can eat without seeing each other). I let them play in the morning and evening but I'm always close by to supervise. If I'm not in the same room and I hear a "yip!", I rush into the room and they both freeze like statues – staring at me. I've gotten in between them a few times during play, but I think it was because I'm so paranoid about one getting hurt. I've NEVER heard either one of them growl, no low barks, no hackles raised, and usually they take turns chasing each other – I'm just always worried it's going to get to *that point* and I stop it before it does. We take a group walk when I go home on my lunch break, and then I take them for individual walks in the evening. Both are very cautious of other people but LOVE to go face to face with other dogs. They're pending their last vaccine and both recovering (again) from giardia so we've been very limited where we can go. My plan is to enroll them in separate obedience classes and start taking them on outings one at a time ASAP, but of course their health issues have been a huge impediment.

    One of the trainers I reached out to suggested not allowing them to play with toys together. I was allowing that at first but took them away. I guess it's a major cause of resource-guarding and can be something for them to get aggressive over? I feel like that could happen with any set of dogs – littermates or not – but I'm not trying to push my limits here. So, I set up a divider in their bedroom and I've been letting them play with toys separately, but they can still see each other. They each have the same exact toy and same exact Nylabone when they are separately playing, but they can see each other through the divider and often try to bust through to get at the other. Am I egging on aggression by letting them see the other have fun? Or do they need to just get used to it?

    I take them out for potty breaks at the same time after they've been in the crate for a while – first thing in the morning, first thing when I go home on lunch, first thing after work, middle of the night. The rest of the potty trips are separate throughout the day. One of my girls hasn't had an accident in two weeks so I always take her second. The other is having an AWFUL time. We had two accidents just this morning within a half hour. She's been tested for a UTI and given antibiotics for vaginitis so I'm fairly positive this is not a health concern. I think she's drinking more water than she needs because she's worried there won't be any left for her? She will take a drink, then her sister will take a drink, and she goes to take another drink. They were homeless early on so I think there's a scarcity fear in there somewhere. She also tries desperately to eat poop. Anyway, she needs more frequent potty breaks than her sister but the only way I know to do that is to confine her sister to a crate or the bedroom – otherwise she is dying to follow us outside. I just don't want her to feel like she's being punished for having good bladder control. Thoughts?

    In addition to separate walks, I have been working on separate obedience training on my own and then we practice the commands throughout the day together. They are learning really well – sit, down, paw, high five, stand, off, come, wait. Unfortunately I have been doing a lot of the separate obedience training outside because when I take one and leave the other in her crate, she cries for a while. It's not every time but most of the time. Usually I can hear it taper off after a few minutes but sometimes it goes on until she hears us come back into the house. I don't know if it's them being separated as much as it's her being completely alone, because the one I'm with NEVER acts upset about being away from her sister. Although whoever I have with me sometimes gets so concerned that her sister is crying, that she will do everything she can to get back to her. I was taking one down in my basement (it's finished) to play with toys with me, leaving the other in a crate with either a stuffed Kong or a bully stick. The novelty of the "busy toy" wears off quickly or doesn't work at all in distracting her from our absence. No one has made themselves sick or been destructive while I'm out with the other, but I know they both get upset and it makes me sad / makes it difficult to really enjoy bonding time with the other. I will take ANY suggestions on this one. If I can get this down, I think we'll be golden.

    Anyone know at what point we can stop the separate everything? Is there an age where, if you hit it, you're basically in the clear? Will these puppies ever calm down and stop riling the other one up? Lol. I'd love to hear some hopefulness!!!

    1. Hi Arielle! You are doing great. You can absolutely let them share toys. The bigger issue we typically see is the hyperattachment, so you're doing a great job of giving them separate time and spaces. Things tend to get easier around 12-18 months of age. Hang in there!

  31. I was strongly considering adopting 2 year old adorable Cotons, male/female littermates. They regretfully need to be rehomed because the owner has deteriorating health. Unfortunately, they brought them home as new pups right when the pandemic started and haven’t had proper socialization. And one owner has been working from home so they’ve mostly been with her. Her partner is in the medical field and works long hours outside the home.

    After speaking at great length with the owner, she told me this and also how they have a fear of people, especially the female. Other new dogs need to be gradually introduced to them. But she said if someone comes to the door they bark and bark and it’s almost like they don’t want anyone in their house. They have to be removed from the room. Or introduced to people VERY gingerly, some get down on the floor with the dogs at first. Again, she said it’s mostly female who has these issues and is also the alpha of the two, even though smaller. Stubborn and doesn’t want to always follow commands. Bossy. When she gets excited as in fear, she’ll poop while jumping around anxious.

    The two dogs are definitely very bonded and when one acts up, the other follows suit. They can’t walk together because they can’t have other people or dogs around or they go berserk.

    The owner said they’re trying to get a trainer in but with the pandemic it’s been difficult. The male actually sounds like he would be easier to train. Anyway, after hearing all of this, I was honest with her and said as much as I would love to take her precious dogs into our home, I also let her know that I don’t feel that my husband and I are up to taking on the challenge of training and raising bonded littermates with fear issues. We have two small grandchildren who are very gentle, but the dogs have never been around kids. Or really not men on a regular basis. I’m just concerned that the dogs might react around our grandkids or even with my husband.

    I’m going to be 71 next month and not quite as patient or energetic as when we had a Coton of our own as a new pup until age 13+. It was also easy to have our medium sized rescue mix we adopted from a shelter at age 1. We said goodbye to him at age 16.5 this past August. :( So we’re experienced dog owners and have even had two at once but very different ages.

    So, do you think I’m right by not wanting to take on these adorable little Coton de Tulears who are bonded littermates without socialization and fear issues? If she was willing to rehome them separately I would take the male. He’s easier going from what she said. But she’s adamant about having them adopted together. I sure hope there’s someone out there who has the patience and expertise to give these pups a home. I know their owners are devastated to have to rehome them. I just need reassurance that I’m doing the right thing by passing them up and not just a wimp because I’m not sure we can take this challenge on. I feel bad because I can’t take them, but I also realize I’ve gotten a bit lazy in my old age. ;) Thank you!

    1. You are so kind to try to help these dogs! I know it can be difficult to say no to helping both of them, but this would be an extremely challenging undertaking, and it sounds like the dogs would benefit immensely in the long-term from having separate homes (maybe they could have regular playdates!) But it sounds like you are making the right decision for your lifestyle and what you're looking for.

  32. we have springer spaniel brother and sister 6 months old. He has become aggressive towards her and she is scared of him a lot of the time. We are working with a springer rescue to find the male a home. We are devastated and there is a lot of crying going on in our house but I feel it is much better for them to be separated so they can both live happy lives then to keep them together in this situation. It is not going to be easy but I know it is the right decision. I would recommend finding a rescue organization for your dog. The springer rescue has a waiting list of carefully screened families so this is a good option. I feel its selfish of us to keep the dogs just because we will be sad when the situation may only get worse with time.

  33. Sorry as I know this is an old blog post. But in your professional opinion, once some of these behaviors have occurred, is it absolutely impossible to reverse or improve them? I have 21 month old littermates, both males. They are rescues, we didn't know anything about littermate syndrome when we adopted them at 2.5 months. Didn't follow any of the separation protocols listed above, but we took them to group training classes for the first many months. They developed reactivity around 6 months (one more than the other). So I started to do separate walks and found that the one who reacted less was really quite fine on his own.
    But when we moved countries is when their behavior became very hard to manage. One developed separation anxiety from us (now worked on it through desensitization and can be alone with his brother for 4+h). Aggression is not really a problem; this year alone they have had maybe a handful of scuffles (never lasts more than 2 seconds, never resulted in biting or a fight, just a lot of noise/screaming, different to when they play) and its usually when we haven't been careful enough with for ex. one finishing his chew before the other (we separate when feeding). We don't have them crate trained, and it is not advised for the fearful one to be crated because his SA is connected to confinement anxiety.
    The biggest issue is that the one with SA this year started refusing walks on his own. This makes working on reactivity very hard because we have to take them out for potty. We are working with an R+ trainer, and actually the reactive one is doing so much better because we go on group walks and I know we can reliably calm him down around triggers in the future. However, since he has to go out with his brother to potty, all the work gets reversed. The reactive one is noise reactive as well and barks a lot at home. They both bark at people coming into the house but then calm down and usually accept snuggles within the first hour of a stranger coming. They are fine with sleeping and calming down for the majority of the day, but generally get overexcited with new situations very easily.
    Long story short, I feel very guilty for unknowingly harming my dogs in this way and I would really love to help them out, but not sure if this is even realistic. We are planning to put the more fearful one on anti-anxiety meds come the new year and hope this will ease him into the desensitization process…

    1. It sounds like you're doing ALL the right things! It sounds like they really enjoy one another's company and you haven't harmed them in the slightest. You will likely find that the anti-anxiety medication is going help immensely with the fearful dog's ability to cope outdoors. I would try, if possible, spending some time outside without the pressure to use the bathroom. Go outside (even if you can't make it past the doorway at first) toss some excellent treats, and then retreat back inside. Gradually work your way further and further out as your dog gets more comfortable. Would love to hear an update in a few weeks!

  34. We have two Labradors male and female from the same litter. They are now 8 months and also have the company of our 2 and a half year old mixed breed female. They all get on really well and mix with other dogs well when out walking or they visit our home. Our lab bitch will be sorted in January but just noticed a few spots on the flooring so guess she will need to get over this first. They do play quite a bit and our older one joins in. Never gets out of hand though. (Well not yet).

  35. I have two twin puppies agirl and boy, the boy has had intercorse with his sister not know they are siblings, and he won't stop he keeps charging at her like a bull at a bull fight. So what can I do to stop this.

  36. I have two littermate brothers. They are currently 12 weeks old. I am absolutely terrified of the negative effects of littermate syndrome. Since day one we have had the boys in separate crates. We usually have one on one training sessions with them. They eat separately, and we try to have separate play sessions. Separate walks etc. They listen and follow commands very well. When they are playing together they can get pretty rowdy. I just want to ensure they never get aggressive with each other. They currently play with the same toys together. How can I ensure that later down the line, aggression is not a factor. I’ll take any advice can get.

    1. The advice in our blog gives our main recommendations to help prevent littermate issues – it sounds like you're doing a great job! Rough play is normal – we just watch that it doesn't spill over into overarousal/aggression.

  37. We currently have two 12 week old littermate brothers. After reading everything about littermate syndrome I have become very nervous about my decision. However since day one we have tried to separate them as much as possible. They currently sleep in separate crates. They go on walks separately, train separately, eat separately etc. However we do allow them to play with each other throughout the day. As they are getting bigger we have noticed that they have become more rough during playtime. Nothing has gotten out of hand. I just want to ensure the negative effects of littermate syndrome do not have an impact on them as they continue to grow. What is the fine line between aggression, and fun play? We are trying are best to treat them as individuals. We never want them to get too aggressive or codependent on each other. Any advice?

    1. We have many clients with successful littermate households! It sounds like you're doing a great job giving them separation from each other. Rough play is normal – we always look for a give and take to the play and not just one dog overtaking the other. You can teach a positive interruptor word that recalls the dogs back to you if they're getting too overstimulated. Working on a blog about this!

  38. I have recently taken home a 8 week old female red fox lab. Our friends have taken her sister home. We reunited them after a few days apart and training separately in our own homes, and they initially engaged in rough play but it quickly escalated to what I thought was full aggression/ fighting.

    We can see they both want to play but then one attempts to mount the other to become dominant. They take this in turns before it breaks out into a full fight. They’ve met 3 times now after this incident, and it’s still the same. They’re 11 weeks now.

    Do we let them figure out who is dominant? They both get on beautifully with other dogs.

    1. It would be rare (although not impossible) to see true aggression at this age between siblings. I would strongly recommend professional guidance to observe the dogs' interactions as I can't say for sure without observing directly.

  39. Hi, have 2 rehomed male littermates that are untrained and causing mayhem in our house. I was thinking of rehoming them separately. Is this cruel? I feel they would flourish if given the chance to be independent of one another. They have already ganged up and bitten my female.

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