12/13/2025
Littermate syndrome describes behavioral problems, like extreme codependency, fear, or aggression, that can arise when two puppies, often from the same litter, are raised together and fail to properly socialize with humans or the wider world, instead forming an overly intense bond with each other, which hinders their individual development and increases risks like separation anxiety and resource guarding. It’s less a formal diagnosis and more a result of mismanagement, where owners focus too much on the pair and miss crucial individual training and socialization, leading to heightened anxiety and difficulty coping when separated.
Common Behaviors & Issues
Codependency: Puppies rely heavily on each other, leading to separation anxiety when apart.
Fear & Aggression: They may become fearful or reactive to new people, dogs, or environments because they lack individual socialization.
Resource Guarding: Unhealthy competition can develop over food, toys, or even people.
Difficulty with Training: Individual training is often neglected, making it harder to teach basic commands or good habits.
We seen it often and unfortunately the dogs get the brunt of it. If a breeder is open to selling you littermates - run away.
