Littermate Syndrome (and why we do not adopt out puppies in close ages at the same time)

Littermate syndrome most commonly affects dogs between 8 weeks and 18 months old. This condition is observed in puppies from the same litter (or even unrelated puppies of similar ages) raised together. The key developmental stages when littermate syndrome issues tend to emerge include:

8–14 Weeks (Socialization Period):
Puppies become overly dependent on each other.
They may struggle to bond properly with their human caregivers or learn basic social skills.

4–6 Months (Juvenile Period):
Behavioral issues such as fearfulness, separation anxiety, or aggression can start appearing.
Puppies may become anxious when separated from each other, even briefly.

6–18 Months (Adolescence):
Issues such as lack of focus during training, fear-based aggression, or inter-sibling aggression may develop.
The puppies' bond with each other may inhibit their ability to mature independently and form healthy relationships with humans or other dogs.
While these ages are the most critical, the effects of littermate syndrome can persist into adulthood if not addressed early.

Littermate syndrome can affect puppies that are close in age, typically within 4–6 months of each other, even if they are not from the same litter. The risk increases when puppies are:

Adopted Together: Two puppies of the same age (littermates or not) brought home simultaneously are more prone to forming an excessive bond, leading to littermate syndrome.

Born Within a Few Weeks of Each Other: Puppies born within 2–3 months of each other can also develop similar behavioral challenges if raised together in the same household.

The key factor isn't necessarily being siblings but the similarity in developmental stages. Puppies of the same age tend to form a strong reliance on each other instead of developing individual independence and bonds with their human caregivers.