Littermate Syndrome: Fact or Fiction?My Experience as a Trainer, Breeder, and Littermate Owner

by Maureen Cucinella Certified Professional Dog Trainer, Breeder, and ownerof Spirited K9 in Blue ridge, GA

Littermates - Connie and Kramer

If you’ve spent any time in the dog world—especially online—you’ve probably heard the warnings:

“Don’t get littermates. They’ll bond with each other, not with you.”“They’ll fight when they get older.”“They’ll develop behavioral problems you won’t be able to fix.”

The list goes on.

So… is any of that true?

I’m a professional dog trainer, a breeder, and I personally own littermates. I’ve heard all of the arguments—and I’ve also lived it. I’d like to share what my experience has been like and what I’ve learned from raising a pair of littermates in my own home.

What is littermate syndrome, anyway?

It’s not a diagnosable illness. “Littermate syndrome” is a term used to describe a group of behavioral issues that can occur when two puppies from the same litter—or two puppies of similar age—are raised together in the same household.

The issues might include:

• One puppy becoming overly dependent on the other

• Anxiety when separated

• Delayed or stunted social development

• Increased fighting or competition as they mature

  
  

Sometimes the dogs become anxious and can’t be separated. Other times, they start fighting around the one-year mark. Regardless of how it shows up, it’s rooted in the same core issue: not enough individual structure or guidance during development.

Do I believe littermate syndrome is real?

Yes—because I’ve seen it. I’ve worked with clients whose dogs couldn’t function unless they were together, and others who ended up rehoming one because of intense aggression between the two. It’s not a myth. But it’s also not inevitable.

Do my puppies have littermate syndrome?

No. My dogs have grown up together and do not show any of the behaviors typically associated with littermate syndrome.

So, what’s the difference?

How I raised them.

From the beginning, I made sure to prevent the issues that tend to lead to littermate syndrome. Here's what I’ve found to be most important:

1. One-on-one time is non-negotiable.This is where most people slip up. It’s easier to walk them together, train them together, and do everything together—but that’s exactly what causes over-attachment and insecurity. Each of my pups got their own time with me, every day. One would stay home while the other came out for training or errands. It’s not easy, but it builds confident, independent dogs.

2. Constant supervision is crucial! Owners often let littermates roam together unsupervised, thinking they’re “keeping each other busy.” But as the dogs mature, competition naturally increases. Fights over food, toys, or just excitement can become a pattern. I never relied on my puppies to babysit each other. They were supervised, separated when needed, and taught how to coexist with boundaries.

3. Don’t treat them like human siblings.It’s natural to want to think of our dogs like kids—but dogs don’t operate that way. They don’t “need” a sibling. They need leadership and clear communication. When dogs are raised like a pair of toddlers instead of animals with instincts, it can create major issues down the road.

Can littermates be raised successfully?

Yes—but it’s not for everyone.

To do it well, you’ll need to:

• Spend time with each dog individually, daily

• Supervise play and correct unhealthy interactions

• Train them both separately and together

• Let them experience life both with and without each other

  
  

If that sounds overwhelming—or if life gets in the way and you can’t give that level of structure—it’s okay to reconsider. Rehoming one dog, if necessary, doesn’t make you a bad owner.

Do I regret keeping littermates?

Not at all. I’ve had a lot of fun with them. They were raised with clear expectations and plenty of one-on-one time, and they continue to get individual attention. They respect me, they coexist well, and they both listen. But it’s worth repeating: I’m a trainer. I enjoy the work. I knew what I was getting into, and I was ready for it.

As a breeder, would I sell littermates together?

No, I wouldn’t.

Most people don’t know what they’re getting into and often feel trapped after committing to two dogs. I’ve heard of breeders doing “two puppies for one price” deals—this is not something a reputable breeder would offer. That’s a red flag. Raising littermates is double the work and takes more skill than most new puppy owners are prepared for. I’d rather see a family succeed with one well-raised pup than struggle with two and risk rehoming one (or both) down the road.

Are you struggling with a pair of littermates? It may be time to give me a call so i can help give some guidance, or schedule you for a consulation.