Subscribe to our newsletter for FREE pet updates
Thank you! Please check your inbox to confirm your subscription.
Sorry, something went wrong. Please try again.

The Hidden Challenges of Adopting Littermates

Should you ever consider adopting two puppies, or siblings, at the same time? While it may seem like a grand idea, many shelters and breeders don't allow it for very good reasons. Often a disaster waiting to happen, here's what I advise you to do if you've already adopted a pair.

littermate syndrome


  • Most dog behaviorists agree it's a bad idea to bring home a pair of puppies from the same litter, and many shelters and breeders don't allow it
  • The problem is "littermate syndrome" in which two sibling pups adopted together bond intensely with each other — but not to human family members
  • Puppies with littermate syndrome are often very difficult to train, can display extreme separation anxiety when apart, and may develop aggression toward each other
  • If you've adopted a pair of littermates, there are steps you can take to help them grow into well-socialized, balanced adult dogs, but it will require extra time, energy, and planning

Many well-intentioned pet parents decide to adopt two puppies at the same time so they can grow up together. But what they and many other people don't realize is that experts in canine behavior typically discourage the adoption of puppy littermates. In fact, many shelters and breeders refuse to place siblings together.

The reason, according to certified professional dog trainer Jeff Stallings, writing for The Wildest:

"Anecdotal evidence suggests that behavioral issues may arise during key development periods because the two puppies' deep bond impedes their individual ability to absorb and grasp the nuances of human and canine communication."1

Said another way, canine siblings can be so closely bonded on a primal level that if they're adopted together, that deep connection can inhibit their ability to learn how to communicate successfully with their new family and interact with other dogs. They grow up with a "muddled understanding of the world around them," according to Stallings, which can create fearfulness and other maladaptive coping behaviors.

The phenomenon is known as "littermate syndrome," and it doesn't occur in every pair of littermates who are raised in the same home. However, it happens often enough that experts in canine behavior and the human-canine bond advise against bringing home siblings. Signs of littermate syndrome include:

  • Fear of unfamiliar stimuli
  • Fear of strangers (people and dogs)
  • Failure to learn basic obedience commands
  • High level of anxiety when separated even for a short time

'A Disaster Waiting to Happen'

According to world-renowned veterinarian and dog behaviorist Dr. Ian Dunbar, when it comes to raising sibling puppies, "It's a disaster waiting to happen for the littermates because they don't get socialized to other dogs or people, let alone to their owners."2

Many pet parents assume the pups' interactions with one another are adequate socialization, "but when the puppies are five or six months old and meet an unfamiliar dog in a novel setting, they absolutely freak out," Dunbar told Stallings. He also points out that training siblings is especially difficult because they're "wearing blinders to all but each other."

"It's more than twice the work; it's exponential," explains Dunbar. "The two combine to produce levels of energy that we can barely measure. Tension develops in training and compliance as they squeeze the owner out of the relationship. They're always living with an enormous distraction: each other."

Patricia McConnell, applied animal behaviorist and author of several books on canine behavior, agrees. From The Other End of the Leash:

"It's just hard to get their attention. They are so busy playing with each other … that you become the odd man out. I suspect this indeed does have to do with social bonding to some extent, but I have seen pups of a duo who clearly adored their humans. Adored them. They just didn't listen to them.
"It seems harder to get their attention, harder to teach them emotional control and harder to teach them boundaries. I imagine that we humans become more like party poopers that interfere in their fun with their playmates, not to mention that we are more tiring, because they have to learn a foreign language in order to communicate with us."3

Sometimes littermate syndrome takes the form of constant fighting between the dogs, especially same sex pairs. Aggression and bullying are seen more often between siblings than between unrelated dogs, and things can get vicious. Many owners of sibling pairs can recount horrible stories about the harm caused to one dog by the other.

Animal shelter employees have stories as well of pairs (or one of a pair) being returned because the adoptive pet parent feared for the well-being of the sibling being bullied.

Hyper-Attachment Can Lead to Separation Anxiety

Nicole Wilde, canine behavior expert and author of Don't Leave Me! believes separation anxiety between littermates is the result of hyper-attachment, which is also what interferes with the puppies' ability to be properly socialized.

"People assume that having two same-age pups who play together and interact constantly covers their dog-dog socialization needs," Wilde told Stallings, "but they in fact don't learn how other [dogs] play and have no idea about social skills with other puppies, adolescents or adult dogs.
"Perhaps one puppy is a bit of a bully, which his littermate puts up with," Wilde continued, "but his rude behavior might not be tolerated by a new dog in a new setting."4

University of California, Davis veterinary behaviorist Dr. Melissa Bain believes the level of owner involvement is key in determining how relationships evolve between littermates and their adoptive family. "The symptoms escalate when the owners treat them as one dog with eight legs," she told Stallings.

Bain also believes conflicts between siblings may be caused by the dogs' difficulty establishing a natural canine hierarchy, since they are so similar in size, age, and sometimes, gender.

Many canine behavior experts feel it's best to rehome one of the siblings when a pair is showing early signs of littermate syndrome, so that both puppies have the opportunity to grow separately into stable, balanced adult dogs.

Since this can be a difficult time for the original adoptive family, it's often easier to have prospective new owners meet both puppies and decide which one to take.

Planning Ahead for the Best Outcome

It's important to keep in mind that it isn't a foregone conclusion every pair of puppy siblings will develop littermate syndrome. According to Stallings, there is evidence that littermates are more likely to thrive when there's an older dog in the new family who exerts a stabilizing influence on the pups.

Professional dog trainer Pat Miller, writing for the Whole Dog Journal, says there are things you can do to prevent or mitigate littermate syndrome if you've already brought sibling pups into your home.5 The goal is to keep the puppies from developing a counterproductive degree of emotional dependence on one another.

  • Two dogs = two crates — Miller recommends crating your puppies separately at night. The crates can be near each other initially, but one pup per crate helps each dog learn to adjust to being alone. The next step is to gradually increase the distance between the crates until the pups can no longer see each other.

    Make sure the crates are in bedrooms at night, so the pups spend several hours in close contact with their human family members.
  • Two dogs = two training sessions — Train your puppies separately so that you can count on their undivided attention. Miller also suggests walking and socializing them separately to avoid ending up with a leader and a follower who looks to the leader instead of you for social cues, commands, and direction. This will help both pups develop into confident, independent adults.

    Use training sessions to lavish attention and affection on one puppy while the other works on a treat-release toy in his crate in another room. This will allow you to develop a bond with each puppy.
  • Two dogs = two play sessions — Miller suggests separating the pups for play sessions at least some of the time so the less assertive of the two can gain confidence.
    "For example, if you always play 'fetch' with the two together," says Miller, "you're likely to see that one pup repeatedly gets the toy and brings it back, while the other runs happily along behind. If you watch closely, you may even see the more assertive one do a little body language warning if the other tries to get the toy — a hard stare and stiffened body, perhaps.
    "The less assertive one defers to her sibling by letting go of the toy and looking away. That's a fine and normal puppy interaction, but it can suppress the 'softer' pup's retrieving behavior.
    "Unless you make the effort to give her positive reinforcement for fetching toys when you play with her alone, you might find it difficult to get her to retrieve later on in her training."6

One Pup at a Time

As I mentioned earlier, littermate syndrome isn't inevitable for every pair of puppy siblings. Genetics play a role, as does the knowledge and commitment of the owner to raise two well-socialized, balanced individuals.

However, the general advice given by professionals is, don't do it. Instead, adopt a puppy who is most likely to fit into your lifestyle and then focus on training and socializing your pup to ensure she's comfortable in her environment and during encounters with other dogs and people.

Only after your puppy has grown into a well-balanced adult is it smart to think about adding a second canine companion to the family.

Most Recent