You’re thinking of adding a new puppy to your family. In fact, the puppies are so cute that you may even be tempted to adopt two at once. But wait! Before considering adopting two puppies from the same litter, you should be aware of the challenges that it may present.

In addition to having to scoop twice the amount of poop, adopting and raising two puppies at the same time can lead to behavioral issues, such as “littermate syndrome.” In this article, we will discuss everything you need to know about the behavioral issues associated with littermate syndrome and how to prevent it.

What Is Littermate Syndrome?

Two puppies next to each other

  • Littermate syndrome may cause anxiety and aggression in puppies raised together.
  • Behavioral issues often stem from inadequate individual care, not just close bonding.
  • Separate training and socialization are key to preventing littermate syndrome.
  • Proper intervention can help resolve littermate syndrome over time.

Image source: Ben Michel

Littermate syndrome, also known as littermate dependency, is described as a set of unwanted behaviors that occur when two puppies are raised together simultaneously. This “syndrome” can occur with sibling puppies or with two puppies from different litters who are close in age.

The belief is that if two puppies are raised together shortly after being weaned from their mother, they may develop behavioral problems like fear, anxiety, and aggression.

Littermate syndrome is a term often used to describe certain behavioral patterns in two puppies raised together. These may include anxiety when the pair of pups is separated; fear of unfamiliar or new things, people, and situations; and aggression towards one another, especially starting around the age of sexual maturity. However, “littermate syndrome” is not recognized by veterinary behavior specialists as a true syndrome.

For the purposes of this article, we will refer to the behavioral issues that may come with raising a pair of puppies as littermate syndrome. But in actuality, the behavioral problems associated with this syndrome do not necessarily seem to be a direct consequence of raising two puppies or littermates simultaneously.


Rather, they seem to be due to the extra work and difficulty that come with raising two puppies instead of just one puppy. After all, raising one puppy, let alone two requires a great deal of time and effort.

Littermate syndrome assumes that two puppies raised together during the socialization period will bond so intimately that their ability to bond with their human owners is impeded.

While this may be true to an extent, the behavioral problems associated with littermate syndrome seem less to do with the dogs’ ability to bond with their owners and more to do with the owner’s ability to provide sufficient individualized care to both puppies.

What Does Littermate Syndrome Look Like?

Two husky puppies playing with each other

Image source: Mihaela Pastiu

The socialization period, when puppies are 3 to 12 weeks of age, greatly influences dogs’ behavior long-term. During this period, puppies begin to explore new surroundings and learn social cues. As part of social development, this is the period during which puppies become interested in interacting with people.

However, dogs with littermate syndrome may rely more heavily on each other and be less likely to defer to their owners for reassurance or reinforcement of behaviors. These dogs may reinforce each other’s undesirable behaviors and ignore their owner’s instructions.

As a result, signs of littermate syndrome include codependency, over-attachment to each other, aggression, and separation anxiety. These dogs may also exhibit fear aggression, leash reactivity, and neophobia (fear of new people, places, things, and situations). Additionally, one of the puppies may be more aggressive and dominant whereas the other may be more withdrawn and submissive.


How to Prevent Littermate Syndrome

Preventing littermate syndrome is important so that dogs don’t develop behavioral problems or need to be rehomed. The easiest way to prevent littermate syndrome is to refrain from adopting two puppies from the same litter or two puppies of the same age at the same time. However, if you have already adopted two puppies at once, there are some strategies you can implement to prevent littermate syndrome.

A good first step as an owner is to familiarize yourself with canine body language. Understanding a dog’s body language will facilitate training and help you identify any anxiety or other behavioral issues early on.

Another important point is to provide enrichment and training to the puppies separately when possible. This includes walking, socializing, and one-on-one attention with you as the owner. Try to do these activities with one puppy at a time. This is necessary to get the two dogs accustomed to being apart without becoming anxious.

Owners can implement tools and strategies like crate training in separate crates and muzzle training if necessary. Additionally, pet parents can utilize management strategies addressing environmental considerations. For example, owners should provide multiple sleeping places or beds and separate food bowls.

There are misconceptions about socialization among dogs who live in pairs. It is not sufficient for two dogs to solely socialize with each other; they need to be able to socialize with other dogs. Practice socializing your dogs with other dogs individually and together.

Some people want to raise two dogs simultaneously because they believe playing together will automatically provide sufficient mental and physical stimulation on its own. This is not true. Even pairs of dogs need additional and individual mental stimulation and physical exercise.


Before resorting to rehoming one of your pups, consult your veterinarian or a behavior specialist for professional help if you suspect your dogs are exhibiting littermate syndrome.


Is Littermate Syndrome Guaranteed?

No, littermate syndrome does not occur in all pairs of puppies who are raised together. Plenty of breeders successfully raise pairs of puppies without these undesirable behaviors. Two dogs may be more prone to developing littermate syndrome if they are lacking in socialization with other dogs, individual training time, physical exercise, and mental stimulation.

The best way to avoid littermate syndrome is to avoid adopting two puppies at the same time. However, if you do adopt two puppies at once, you must know how to recognize littermate syndrome so that you can intervene quickly.

How Long Does It Take for Dogs to Bond With Each Other?

There is no set amount of time that it takes for two dogs to bond with each other. Depending on the individual personalities and life experiences of the dogs, bonding could take several weeks to a few months. However, puppies who are between 3 and 12 weeks old may bond more quickly due to the socialization period. In general, dogs will start socializing with each other fairly quickly but it takes time for them to form a true bond.

Does Littermate Syndrome Ever Go Away?

Yes, littermate syndrome can go away with consistent and appropriate training and intervention. However, littermate syndrome won’t go away on its own. Littermate syndrome is essentially a set of unwanted behaviors. Like any unwanted behavior, littermate syndrome requires training in the form of tools like desensitization and counterconditioning. Veterinarians and veterinary behaviorists can serve as great resources in this regard.