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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, 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 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 Rottweiler puppies posing in front of black background. Getting three sibling puppies can set you up for littermate syndrome.

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 to 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 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.

Three Beagle puppies sitting in a basket. Little rascals might develop littermate syndrome if taken home together.

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 dogs’ 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?

About Danielle

I am the founder of PawLeaks where I share weekly tips on dog training and behavior. Sharing a passion for dogs and helping owners to solve problems through understanding canine behavior and modification is my number one goal.


Saturday 16th of July 2022

We recently went for one Golden Retriever pup and ended up leaving with 2 females at 8 weeks old (now 12 weeks old). I had never even heard of littermate syndrome until tonight and now I’m panicked! They both have very different personalities - one more aggressive and feisty, and the other laid back and loving (quintessential GR personality). I just started crating them and am going to start feeding them separately, and taking them out separately as much as possible and we start puppy classes in September. My concern is they do (play?) fight. I assumed this was typical puppy behavior, but now I question when to know when it’s too much, and anytime I see them wrestling around, do I break it up? More so than anything else I am now worried about aggressive behavior as I do have a toddler in the house!


Monday 18th of July 2022

Hi Jessica, playing together is part of normal puppy development, it's usually not necessary to break up play, on the contrary. It's only necessary if play gets too rough (i.e. one signals that she doesn't want to play anymore by whelping, cowering, etc.). Puppy play classes are great so they have contact with other dogs too.

If they're doing well and you train them consistently, you'll probably have nothing to worry about. It's good to incorporate 1-on-1 sessions but don't get too worked up over them being together. Teach your toddler how to behave around the pups and the pups how to behave around your toddler. Aggression doesn't develop out of nowhere if you properly socialize your dog and rely on positive reinforcement instead of punishment.

Cheers, Danielle


Wednesday 6th of July 2022

We have 3 American bullies. They are brown and the other is lilac, the oldest 16 weeks is blue.They are comparably the same age. All from different litters. But 2 were crated and the other was with another litter. Anyways the two younger that were kenneled together, 1 of them (brown) would prefer to play by himself when other is kenneled. They all 3 fight playing, although i feel it get serious. We lead train and stack separately. They are 14 and 16 weeks old. They still prefer to play with each other, the 16 week old is pretty bigger then the others. The Lilac prefers people, the blue prefers either, the brown is the only one who would also rather be in his kennel playing with toys. Is this normal and just part of their personalities


Thursday 7th of July 2022

Hi Stephanie, it's totally normal that every pup has a different personality (i.e. preferring toys over people for now or vice versa). That being said, playtime and socialization is crucial for all of them and they definitely should display healthy behavior with each other. Extremely rough play should be discouraged, especially if the others are clearly not into it.

Usually, the mother will have taught them that as well as basic bite inhibition which they partly learn within the litter. It's unclear where exactly all of them are from, but why don't you consult their breeders, maybe that'll shed some light on their behavior.


Friday 3rd of June 2022

So we have 2 dogs who mated and had 5 pups. We are unable to recommend 2 pups and its likely they'll be staying with us. They are beginning to enjoy play with their parents and love time with us as a family. Individually and together. They are just 8 weeks old now and need to know best ways to discourage litter mate syndrome. They all play fought together and the 2 remaining still do though are (so far) content on doing own thing exploring round house. Will nap separately. Though sleep together at night. All advice appreciated


Tuesday 7th of June 2022

Hi Deborah, apart from what's recommended in the article, there's not that much you can do. Occasionally training or playing with them separately and making sure they seem to have a healthy relationship is all you need. Keeping them is the only responsible option anyway unless you manage to find the perfect home for them but never settle for anything less due to a potential issue that might never arise.

Cheers, Danielle


Saturday 30th of April 2022

We have two, three year old Aussies. We went for one and accidentally came home with two as they were so little and cute. We love them both, but even now they occasionally fight. Hard. We're not sure what to do. Any tips? We love them both dearly, but don't want to see them hurt (or worse). Please help.


Sunday 1st of May 2022

Hi Kristi, it'd be important to know what your dogs are fighting over and how exactly they behave. Has this issue been present from the get-go or just developed recently? I'd suggest consulting a trainer.

Sometimes, it's just rough play between littermates but if it persists and happens around resources such as toys, food, favorite people, etc. then that might need to be addressed.


Thursday 17th of February 2022

We adopted two pit bull puppies. One of them is deaf and had learned to rely on her brother so we didn’t want to separate them. But training has been impossible and now they are very aggressive toward each other but still will freak out if we try to separate them. I’m so frustrated I don’t know what to do. They basically have to stay in their crates if they aren’t outside or they are destructive or fighting. I know they’re not happy living this way, but I don’t know what else to do with them.


Thursday 24th of February 2022

Hey Paula, first of all, you're right in saying that letting them stay in the crate won't solve it. Dogs need mental and physical exercise and also bonding time.

It really depends on how they display aggression towards each other (circumstances, body language, triggers, etc.). Since they're still pups, it's best to train them quickly and for that, I'd suggest you consult a local behaviorist/trainer.