LITTERMATE SYNDROME

"They are all so cute, let’s get two!”

When puppies from the same litter or of similar age are raised together, there’s a risk of littermate syndrome. What is littermate syndrome?

Littermate Syndrome (Sibling/Littermate Aggression ) is an umbrella term that refers to a whole host of behavioral issues that tend to present when puppy siblings are raised in the same household, or puppies within 6 months of age in similarity.

These main behavioral issues can include (there’s a lot more as well):

  • The shy puppy becomes even more shy, withdrawn and completely dependent on the bolder sibling

  • When separated, the siblings on their own become nervous, fearful, and uncertain.

  • The puppies become extremely co-dependent, and high anxiety when separated.

  • They often bond to each other and not the family

  • They generate an enormous amount of energy between them, working each other up and then destructive behaviors can set in

  • When the puppies mature into adults, there are often serious and/or fatal fights to break out between them.

  • And most devastatingly is the affect of when one sibling dies, it can be catastrophic for the sibling.


If you plan to get littermates or similarly aged puppies, there are steps you can take that will most likely prevent these things from occurring. It takes a daunting amount of work on the part of the pet owner.

  • They must be crated, fed, walked, and trained separately.

  • They must have their own socialization sessions and confidence building sessions.

  • They must have separate playdates with other dogs as well as their owners that do not include their siblings.

Overall, it’s best if you do not have siblings or puppies within 6 months of each other to prevent these issues from occurring. Many breeders will not place siblings into a home without the pet owner having a full understanding of the consequences, and extensive education on littermate syndrome to be prepared for the extra work involved.

Here’s some additional reading material:

https://thebark.com/content/dont-take-two-littermates

https://peachonaleash.com/littermate-syndrome-dogs/

https://www.thehonestkitchen.com/blog/what-is-littermate-syndrome/

https://moderndogmagazine.com/articles/littermate-syndrome/80050