Littermate Syndrome in Dogs

You’ve gone to the shelter and you’re smitten. Two adorable puppies with soft, innocent eyes are stealing your heart. They’re siblings and inseparable, tumbling over each other, giving you those pleading, “take me home” eyes. You can’t bear to separate them, and so the decision is made: you’ll adopt them both.

However, as time passes and the initial charm and cuteness fade away, you start noticing some peculiar behavior. They are inseparable, yes, but to the extent that they cannot do anything without the other. They become anxious when separated, even for a short period. Training them seems impossible, and they seem to lack a connection with you, despite your best efforts.

You could be dealing with what’s known as ‘Littermate Syndrome’. It’s a phenomenon that’s not well-known but something every potential dog owner should be aware of, especially those considering adopting two puppies from the same litter. It’s essential to understand this syndrome to ensure your puppies grow into well-behaved, balanced, and happy dogs.

What is Littermate Syndrome?

Littermate syndrome is a behavioral issue that often occurs when two puppies from the same litter (or two puppies of the same age) are raised together beyond the typical weaning period and develop a deep bond. The puppies become so strongly bonded to each other that they struggle to function independently. That bond can also overshadow their connection with their human family. This attachment can lead to a host of problems, from training difficulties to severe anxiety.

Not all siblings raised together will develop littermate syndrome. However, the risk is significantly higher, and the potential problems can be serious enough to warrant caution. Littermate syndrome doesn’t just occur in biological siblings. It can also affect puppies of similar age who spend a lot of time together, especially during their crucial development stage, which is typically the first six months of their life. 

It’s important to note that littermate syndrome doesn’t imply that the pups don’t love or bond with their human family. They do, but their reliance on each other can make them less eager to interact with humans and other dogs, which can hinder their social development.

Signs of Littermate Syndrome

So how do you know if your puppies are developing littermate syndrome? There are several signs to watch out for. The most common one is inseparability. If your puppies can’t stand to be apart, even for a minute, they might be showing signs of littermate syndrome. This acute separation anxiety can manifest in destructive behaviors, such as chewing furniture or excessive barking.

Another sign is aggression towards each other, especially when it comes to resources like food, toys, or your attention. This aggression can escalate quickly and may result in fights. 

Littermate syndrome can also lead to fearfulness or aggression towards other dogs or people. This is because the puppies have not been properly socialized with others; their entire world revolves around their sibling. If your puppies seem excessively shy or fearful around other dogs or people, it could be a sign of littermate syndrome.

Another common symptom is difficulty in training. The puppies are so focused on each other that they struggle to engage with humans, making it hard to train them. They may not respond to their names, basic commands, or even positive reinforcement techniques.

Preventing Littermate Syndrome

The best way to prevent littermate syndrome is by not adopting two puppies from the same litter or of the same age at the same time. If you have your heart set on adopting two puppies, consider adopting them several months apart. This allows you to focus on training and socializing each puppy individually before introducing a new pup into the mix.

However, if you’ve already adopted two puppies, don’t worry, all is not lost. There are several strategies you can use to prevent or manage littermate syndrome. The most effective one is to separate the puppies as much as possible, spending time with each puppy individually. This means separate training sessions, separate playtimes, separate walks, or even separate living spaces. This allows each puppy to develop their personality, confidence, and independence. It also strengthens their bond with you, which is crucial for their development and well-being.

It’s also important to socialize the puppies with other dogs and people, allowing them to experience a world beyond their sibling. This can help in mitigating the symptoms of littermate syndrome and ensuring more rounded, sociable, and well-behaved dogs.

Treating Littermate Syndrome

If your puppies are already showing signs of littermate syndrome, it’s important to take action quickly. Start by implementing the strategies mentioned above – namely, spending time with each puppy individually and working on their training and socialization separately.

If the symptoms persist, consider seeking the help of a professional dog trainer or behaviorist. They can provide you with specific strategies and techniques tailored to your puppies’ needs. Remember, the goal here is not to break the bond between your puppies but to ensure they can function independently and have a healthy relationship with you and with other dogs.


While the prospect of bringing home two puppies at once can be incredibly appealing, it’s vital to be aware of the potential pitfalls. Littermate syndrome can lead to a host of behavioral issues that may be challenging to manage and distressing for the puppies. But with patience, consistency, and the right strategies, it’s possible to raise well-adjusted, happy dogs together. 

Remember, every puppy deserves the chance to shine on their own, to develop their unique personality, and bond with their human family. And as responsible pet owners, it’s our job to provide the environment that allows them to do just that.

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