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Littermate Syndrome: Real or Myth?

Imagine getting two cute, adorable puppies from the same litter and bringing them home to be a part of your family.

You might think you’re doing a fantastic thing, keeping brother and sister pup together.

Cuddling will be double the fun!

I actually sort of considered getting two Rottweiler puppies but am supremely satisfied with just my female Rottweiler Amalia.

Another couple actually got a male and a female from the same litter, but dangers lurk behind doing this.

However, there’s a potential monkey wrench in your best-laid plans.

If you choose two sibling puppies, then you could face challenges due to littermate syndrome.

Littermate syndrome describes the phenomenon when two puppies from the same litter grow up together in the same home.

The puppies get so attached to each other and form such a deep bond, it can spark behavioral issues.

Unfortunately, it can also prevent your puppies from bonding with you, leaving you feeling a little bummed, to say the least.

Is Littermate Syndrome Real?

While not an exacting scientific or medical diagnosis, the concept of littermate syndrome is very real.

However, that doesn’t mean it’s necessarily a given situation for all sibling pups that you raise together.

As with many things, multiple factors can influence the probability and severity of littermate syndrome.

But, there has been quite a bit of evidence suggesting it is best to avoid sibling dogs.

In fact, in some cases, even unrelated puppies adopted at the same time can exhibit signs of littermate syndrome.

Three Beagle puppies sitting in a basket. Little rascals might develop littermate syndrome if taken home together.
Photo by Jarun Ontakrai on Shutterstock

Therefore, if you want more than one puppy, you risk dealing with several behavioral problems.

The theory is that you adopt puppies during a critical time in their development, around 8 weeks.

This time is the age when puppies can start to leave their mother.

During this crucial time, littermates possess a deep bond with each other, recognizing each other by scent.

When puppies share this strong bond, it discourages them from interacting with their human family.

This lack of interest or interaction inhibits their ability to start understanding canine-human communication.

It can also influence how your dogs react and interact with other dogs.

A lack of socialization caused by disinterest in the environment and perhaps other dogs can potentially lead to behavioral issues as well.

What Age Does Littermate Syndrome Start?

Typically, puppies stay together with their mother until at least 8 weeks.

Between 8 and 12 weeks is when most breeders deem it okay for pups to leave the nest.

If you adopt two puppies around this time and raise them together, you could see signs of littermate syndrome as early as 8 to 10 weeks if the puppies stay together after leaving their mothers.

However, slightly older puppies still less than 6 months of age that are raised together can also experience littermate syndrome.

So, basically, issues can begin as soon as young pups leave their mom but stay with each other, whether it’s 8 weeks or 6 months.

What Are the Symptoms of Littermate Syndrome?

If you’ve adopted two puppies from the same litter, you might start noticing some concerning behaviors.

For example, your pups might whine or bark frequently, seem overly fearful or anxious in new situations, and be challenging to train.

You might also notice your new furry family members paying little to no attention to you.

All these can also be caused by a variety of other (non-concerning) factors or a lack of a proper training program.

Be on the alert for clues the dogs might show through their interactions (or lack thereof) with humans.

Also, take particular note of how the two dogs behave when they are apart and when other dogs are around.

Here are a few possible symptoms of littermate syndrome:

  • The dogs show fear or anxiety toward new people, experiences, and other dogs.
  • Puppies display extreme separation anxiety when they’re away from each other. Potential signs can be excessive barking, whining, pacing, and destructive behavior.
  • The dogs only eat when they are together.
  • You might notice a lack of focus and difficulty with things like training because the dogs distract each other constantly.
  • The puppies only seem to want to play with you if they are together.
  • The dogs might fight with each other or show aggression towards other dogs.

Always take a holistic approach and evaluate all the criteria one after one and check if they could be caused by something totally different.

How Common Is Littermate Syndrome?

Although littermate syndrome is not a guarantee, it’s a fairly common occurrence when you adopt puppies the same age.

In addition, some believe that certain breeds are more prone to littermate syndrome than others.

However, there are no evidence-based studies to back up these claims.

Overall, professionals recommend avoiding adopting puppies younger than 6 months old at the same time.

However, it’s best to be prepared to put certain steps into practice if you insist on doing so.

You’ll need to stay dedicated and consistent if you want to try and avoid littermate syndrome.

Does Littermate Syndrome Always Happen?

In a nutshell, no, littermate syndrome doesn’t always happen. However, a lot depends on environmental factors and how you raise the puppies.

If you don’t make a point to treat them individually, then the likelihood of littermate syndrome increases significantly.

A lot also depends on how soon you start working toward preventing littermate syndrome.

How to Prevent Littermate Syndrome?

Of course, the best way to try and prevent littermate syndrome altogether is to adopt dogs of different ages.

For example, you could adopt a puppy but then select an older dog for your second pup.

Another option that could also be successful is to adopt your dogs at least six months apart.

When you stagger your timeline for bringing home your new pups, your dogs are more apt to bond with you.

Plus, it’s a lot easier for you to focus on helping one dog get acclimated at a time to their new environment.

This idea is a good practice no matter your dog’s age.

However, whether you choose one of these options or move forward with adopting littermates, it’s essential to socialize your puppies properly.

It’s also vital to start your action plan right away; the longer you delay, the more likely littermate syndrome will develop.

Furthermore, it’s critical to treat your dogs as individuals, making a point to spend time with them separately.

Not only does this one-on-one time help ease the effects of littermate syndrome, but it also helps you bond with your dog.

Can Littermate Syndrome Be Cured?

If your dogs are already exhibiting signs of littermate syndrome, all is not for naught.

It will take a lot of dedication, but yes, it is possible to remedy the situation. However, immediate action is best.

The sooner you can start working on a plan to resolve the various issues, the better.

Separating your dogs for training is a significant part of this plan so that you can work with them individually.

Remember, it’s about each dog feeling comfortable and confident in their own skin and with their human family.

However, if your pups already share a strong bond, you may need to ease into the separation gradually.

Again, if you plan to adopt two puppies simultaneously, it’s best to prevent littermate syndrome from occurring in the first place.

Employing the following techniques can potentially help ease existing signs of littermate syndrome.

  • Crate your dogs separately, leaving the crates side-by-side at first and then gradually moving them apart. Eventually, the ideal situation would be to have the crates in entirely different rooms. 
  • Train your dogs separately as well. Plan out a training schedule where you only work with one pup at a time. If you plan to enroll in obedience classes, do two separate classes on occasion.
  • Work on socializing each dog independently; take your dog to public settings, go on a walk, and enjoy some play sessions. Then, repeat the same activities with your other pup.
  • As your dogs start to become more independent, you can gradually ease them into joint activities. Enlist the help of another family member or friend. For example, if you plan to take both dogs on a walk, you handle one and your friend the other.
  • Even as you start to have joint training and play sessions, still maintain individual sessions with each dog as well.

Do Dogs Outgrow Littermate Syndrome?

Without a thoughtful and constructive action plan to remedy behavioral issues, it’s improbable your dogs will simply outgrow littermate syndrome.

If you want to be able to get the situation under control, it’ll be because you’ve allowed them to develop independently and receive proper socialization, not because they’ve outgrown anything.

Besides, training one puppy is hard enough – trust me, I know. Puppy blues times two incoming.

As with anything when it comes to your pets, if you’re concerned about their well-being, talk with your vet.

Have you already adopted two puppy siblings and are experiencing some challenges?

I’d love to hear from you in the comments. If you’ve dealt with littermate syndrome in the past, what are some things that helped you and your pups?

Disclaimer: This blog post does not substitute veterinary attention and does not intend to do so. I am not a veterinarian or pet nutritionist. If your dog shows any sign of illness, call your vet.

About Danielle

Equipped with 5+ years of expertise as a Rottweiler owner, I partner with licensed veterinarians and trainers to share research-backed and actionable advice for you and your furry friend.

Becky Crane

Sunday 30th of April 2023

Hi Danielle, 14 years ago my husband and I brought home 2 puppies born the same week (one cocker and one mini schnauzer) and successfully raised them with no issues (and no clue about littermate syndrome!). We recently said goodbye to the last one and are bringing home 2 new mini schnauzer puppies in 2 weeks. We worked with the breeder to select for a positive personalities and have watched them interact (both played but looked to the human alpha first and most often.). They are not of the same litter but Beverly similar ages.

In preparation for their arrival, I’ve now discovered the littermate syndrome risk. Are there certain personality combinations that work to minimize the risk in addition to all the great advice you share above? We are committed to ensuring they bond with us and have 2 girls to help (10 & 12). Im hoping the approach we took the first time will help avoid issues but am now really worried!

Any help you can give would be wonderful - thank you for the Ana ing resource!


Monday 15th of May 2023

Hi Becky, honestly the best advice is to just keep it natural, involve the whole family (sounds like your husband and two girls are onboard) and take it from there to see if any issues develop. As long as both pups are in harmony with each other and don't share any negative predispositions for any specific traits that the breeder has observed, it should probably turn out fine. Hope you won't get that puppy blues with two of these rascals haha!

Wish you and your family a lot of fun, Danielle


Monday 17th of April 2023

Hi Danielle,

I am looking to adopt a 1 year old dog who is being rehomed BECAUSE of littermate syndrome. How can we support this new dog as she joins our family? Will she be okay and confident without her sister?


Monday 17th of April 2023

Hi Kellie, my advice before getting the pup would be to inquire about why exactly the puppy needs to leave. Were the two siblings brought home together at 8-10 weeks? If so, what issue suddenly arose or has it drastically worsened with adolescence?

Make sure you're up for the task if behavioral issues are involved, especially if you don't really know the person who's giving the pup away.

Other than that, the same as with every dog. Socialization, gradual change, lots of positive reinforcement, and consistent training from day one.

If there are existing issues, the current owner should tell you about them (i.e. separation anxiety) so you can work on them.

Hope that helps, Danielle


Sunday 15th of January 2023

I have two GSD male and female 9 months old, you can't quite tell where one starts and the other one ends. We're working on slowly separating them. Our male isn't too bad but our female is horrendous of your on a joint walk and the male is a head with my partner she will pull me over to get back to him. If you try putting them in separate rooms she will bark and wine and continuisly attack the door to get to him. She is petrified of other dogs and he his more than happy to play with them.


Saturday 10th of December 2022

Hi Danielle, This is a unique situation. I got a male Golden Retriever from a very reputable breeder when he was 8 weeks old. The breeder kept two males from this litter, with the plan of ultimately placing one of them depending on which one showed better conformation. Now they are 4 months old, and she has probably selected the one she will be keeping. I am thinking about taking the other one when he is 5-6 months old. He is already house trained and knows basic (and some advanced) commands, as does my boy. Do I need to worry about littermate syndrome, or is it likely to be a non-issue since they are older? They do play together sometimes for a couple of hours, and have stayed together for a couple of weeks, with no issues. Thank you.


Tuesday 13th of December 2022

Hi Barb, if you keep these tips in mind and the pups get along with each other well, there's probably nothing to worry about. Since there's such a time difference between when the first vs second pup is added, you just have to make sure that it will work between them.


Wednesday 9th of November 2022

I'm considering adopting 2 chihuahua littermates.

I totally understand all the things to do to prevent littermate syndrome, and I have had many dogs in the past, so it all makes sense.

My question (that I can not find the answer anywhere) is how long is the process of getting past the potential of developing littermate syndrome. I'm committed to dealing with the preventative measures (crates, training, walking, socializing, bonding) independently, but how long does this process take?

At some point, I would like them to be able to go on walks it just observing them to know when they're confident in meeting people and remembering their training even when they're together? Am I looking at 6 weeks of teaching independence or is forever?

Lots of sites explain the how, but not the how long.


Thanks, Joe


Thursday 10th of November 2022

Hi Joe, there's no set time frame but you definitely shouldn't worry about it forever. It can take as little as 4-8 weeks to build a solid foundation. Even beyond that, constant training will be required but that definitely does not mean that you won't be able to on walks together etc. Some individuals experience a lot fewer problems.

Personally, I advise people against getting littermates, especially if it's an intense breed. If you want to adopt, it might be even harder since they've already formed certain habits but of course, you might feel like they have a playmate and besides, rescuing both is better than just one.