Understanding Littermate Syndrome and the Risks of Raising Two Puppies Together

Bringing home a new puppy is an exciting, life-changing experience. So it’s easy to understand why families sometimes consider getting two puppies at once—after all, wouldn’t they keep each other company? 

Unfortunately, this well-intentioned idea can lead to serious emotional, behavioural, and developmental issues that many owners never see coming. This is known as Littermate Syndrome, and it’s one of the key reasons responsible breeders do not sell two puppies from the same litter to the same home.

In this article, we’ll explore what Littermate Syndrome is, why reputable breeders won’t send siblings home together, and why purchasing two puppies at once is often a sign of poor breeding ethics.

What Is Littermate Syndrome?

Littermate Syndrome refers to a range of behavioural and developmental problems that arise when two puppies of the same age—usually siblings—are raised together in the same household. While it does not affect every pair of puppies, it is common enough and severe enough that most vets, trainers, and ethical breeders strongly warn against it.

Puppies affected by Littermate Syndrome may develop:

• Over-attachment to each other, leading to separation anxiety when apart

• Fearfulness or nervousness, as they rely on each other instead of bonding confidently with humans

• Aggression between the dogs as they mature

• Difficulty training, because the puppies distract each other instead of focusing

• Delayed social development, including poor social skills with other dogs

• Reduced bond with the owner, as their sibling becomes their primary attachment

These issues often become noticeable around 6–18 months of age—long after the “cute puppy” stage.

Why Two Puppies at the Same Time Is a Challenge

Even for experienced dog owners, raising one puppy requires time, consistency, and structure. Raising two puppies at once means doubling nearly every task, including:

• Separate training sessions

• Separate walks

• Separate crate time

• Individual bonding time

• Managing play to prevent overstimulation or conflict

Many families unintentionally treat the puppies as a “unit” instead of individuals, and that’s when problems begin. What starts out as “companionship” often becomes unhealthy dependence.

Ethical Breeders Do Not Sell Littermates Together

A responsible breeder’s top priority is the wellbeing of their puppies and the success of their future homes. Because of this, ethical breeders will refuse to sell two puppies of the same age to one family—especially siblings.

A good breeder will:

• Educate families about Littermate Syndrome

• Encourage spacing out puppy adoptions

• Ask questions to ensure families have the capacity to care for a puppy properly

• Care about long-term outcomes, not quick sales

A breeder who willingly hands over two puppies at the same time—especially without a thorough explanation of the risks—is showing a lack of responsibility and transparency. It is often a red flag that their priority is profit, not the long-term welfare of the puppies or the family adopting them.

Why Selling Two Puppies at Once Is Irresponsible

When a breeder sells littermates together, they are knowingly placing both the puppies and the new owners at risk of:

• Behavioural issues that could have been prevented

• Overwhelming training difficulties

• Potential surrender or rehoming if things escalate

• Emotional conflict between the pups

• Increased veterinary or behavioural intervention costs

A breeder who cares about their puppies will make decisions that give them the best chance at a successful, stable life, even if it means making fewer sales. Allowing (or encouraging) families to take home multiple puppies of the same age simply does not align with ethical breeding practices.

A Better Approach: One Puppy at a Time

If your family wants two dogs, the safest and healthiest option is to wait 12–18 months between puppies. This allows:

• The first dog to mature emotionally

• Proper training and development

• Strong bonding with the family

• A stable foundation before introducing a second dog

With this spacing, both dogs grow up to be more confident, well-adjusted, and easier to manage.

Final Thoughts

Getting two puppies at the same time may seem like double the joy, but in reality it often becomes double the trouble—and sometimes heartbreak. Littermate Syndrome is real, difficult to manage, and completely avoidable when puppies are placed responsibly.

Families deserve honest guidance, and puppies deserve the best possible start in life. That’s why reputable breeders will always caution against raising littermates together—and why selling two puppies at once is a sign of misplaced priorities and poor breeding ethics.

If you’re considering adding a puppy to your home, choose a breeder who puts the wellbeing of the dogs first. And if you eventually want two dogs, take it step by step. Your future pets—and your peace of mind—will thank you.