Sibling Syndrome in Dogs: What It Is and Why It Matters
When two puppies are raised together—especially siblings from the same litter—there’s often an assumption that they’ll be easier to manage because they have each other for company. Unfortunately, that well-meaning decision can sometimes lead to what’s known as “sibling syndrome” or “littermate syndrome.” This behavioural condition can create long-term challenges if not proactively addressed.
What is Sibling Syndrome?
Sibling syndrome refers to a pattern of behavioural problems that can occur when two puppies—typically siblings—are raised together in the same household without adequate individual socialisation and training. It’s not a formal diagnosis, but rather a cluster of common issues seen in practice, particularly by behaviour professionals.
Signs of Sibling Syndrome
While every dog is unique, the following behavioural signs are commonly observed in affected pairs:
Hyper-attachment to each other – They rely on each other for comfort and become distressed when separated, even briefly.
Delayed social development – Pups may struggle to engage confidently with other dogs, people, or new environments.
Lack of focus on humans – Training can be very difficult because the puppies focus more on each other than on their handler.
Increased anxiety or fearfulness – Particularly when alone or separated, one or both pups may become highly distressed.
Inter-dog aggression – Ironically, despite their initial bond, some littermates begin fighting as they mature—particularly during adolescence (6–18 months).
Why Does It Happen?
Raising two puppies together can inadvertently prevent them from developing independence and confidence. They become a secure base for each other—but this comfort often replaces the healthy attachment that should be formed with humans. As a result, they miss out on the normal social and emotional development that comes with being trained and socialised individually.
This effect can be compounded when owners:
Walk, feed, and train the dogs together
House them in the same crate or sleeping area
Use one dog’s behaviour to manage or interpret the other
Without deliberate efforts to separate their experiences, the dogs become emotionally fused, relying on each other to feel secure and often struggling when apart.
Is It Avoidable?
Yes—but it requires intentional management. If you’re considering adopting two puppies at once (littermates or otherwise), you’ll need to commit to treating them as individuals from the outset. This means:
Separate training sessions: Teach them to focus on you without their sibling present.
Independent walks and playtime: Allow each dog to build resilience and confidence in the world on their own terms.
Solo sleep and rest areas: Encourage them to feel safe and settled without needing to be next to each other.
Individual attention: Build your relationship with each dog separately through games, grooming, and one-on-one time.
It’s important to note that this approach is significantly more work than raising one puppy, and it can be overwhelming without support.
What If You Already Have Sibling Syndrome?
If you’re already living with dogs who are showing signs of sibling syndrome, don’t panic—there are solutions, but they often require the help of a veterinary behaviourist or professional trainer with experience in behaviour modification.
Steps may include:
Gradual desensitisation to separation – Teaching the dogs to cope with being apart without triggering anxiety.
Structured independence building – Helping each dog develop confidence and emotional regulation through targeted training.
Behavioural enrichment and emotional resilience – Using puzzles, scent work, and independent activities to strengthen coping skills.
In more severe cases, one dog may benefit from a short-term stay with another carer to allow for a temporary “reset” and more focused individual work. In rare, intractable cases, some families opt to rehome one dog in order to give both animals the best possible long-term welfare outcome.
Final Thoughts
Sibling syndrome is not inevitable—but it’s a real risk when two puppies are raised together without a plan. As appealing as it might seem to double the puppy joy, doing so without preparation can lead to double the behavioural difficulties.
If you’re facing challenges with littermates or are considering adopting two puppies, seek professional guidance early. With the right approach, it’s possible to raise confident, emotionally stable, and well-adjusted dogs—singly or together.