What’s better than one puppy? Two puppies! Or…is it? Like any loving dog parent, you’ve likely checked our new puppy checklist when welcoming home your little buddy. But you might also have heard of problems like littermate syndrome – which, in the long run, can harm their social development.

In this post, we’re going to cover each of these questions – so you have everything you need for your new bundle (or bundles) of joy. (Including how to prevent an escape attempt.) Let’s get started!

What exactly is “littermate syndrome”? Is it real?

Littermate syndrome – or littermate dependency – can occur when two puppies adopted at the same time grow up together in the same home. (And not necessarily from the same litter.) These sibling puppies might form such a deep bond with each other that they miss out on properly socializing with you, other pets, and people.

So when these two pups must be separated from each other even for a short time, they may:

  • Whine
  • Exhibit destructive behavior (like chewing your slippers or peeing around the house)
  • Bark excessively
  • Or show extreme anxiety in new situations
A litter of Australian Shepherd puppies sitting indoors

Read more: Fearful Dog: Our Expert Reveals Everything You Need To Know About Fear In Dogs

The biggest risk factor for littermate syndrome? If you’re raising sibling puppies of the same age together. (Whether from the same or different litters.)

But thankfully, most experts agree that you can avoid littermate syndrome by getting one puppy at a time. Then, wait a year or two to introduce second puppy to the family.

⚠️ Littermate syndrome is not a medical diagnosis. But most experienced dog parents and veterinarians can attest that it is real.

And one of its worst aspects? Your pups might not get to properly bond with you.

And isn’t that the whole reason you got a dog in the first place?

At what age does littermate syndrome start?

If you’ve adopted puppy siblings and keep them exclusively together after 12 weeks of age:

  • They may become each other’s “security blanket.”
  • Because of this, they might miss out on a critical phase of social skill development. (I.e., being able to handle being by themselves – which, over time, may cause them separation anxiety.)
A woman cuddling a black and white puppy

Read more: Separation Anxiety In Dogs

How is littermate syndrome connected to dogs running away?

⚠️ Fear and separation anxiety are two of the most common reasons why dogs – including puppies – run away from home.

And since they’re small, weak, and their senses haven’t fully developed, your little buddy might not be able to find their way home by themselves.

Two puppies with littermate syndrome running through an open field

So make sure you’ve gotten your puppies microchipped (around 8 weeks) to help a vet or local shelter identify them if they get lost.

💡Plus, you could track your wandering puppy’s every step in real-time with a dog GPS tracker – and find them safe and sound, just in time.

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Is littermate syndrome common?

Yes, littermate syndrome can be quite common – especially if you’re raising a pair of similar-age puppies together. But since it’s not an official diagnosis, it’s not a guarantee you’ll come across it even if you’re raising two puppy siblings together.

  • If your little buddies don’t get enough time apart, it could lead to them not properly socializing with other people and pets.
  • And the great news is, it’s 100% possible to avoid littermate syndrome with a little hard work, training, and consistency.
two back and white husky puppies playing with each other against a brick wall

What are the most common symptoms of littermate syndrome?

When your raise two puppies together beyond three months (or 12 weeks) of age, they can become overly dependent on each other.

  • These pups can become so deeply bonded that they live in their own little sphere of safety, separated from the outside world.
  • The attention they give each other is so intense that they can fail to live independently or interact appropriately with other dogs or people.

Here are some of the most common symptoms of littermate syndrome:

Extreme co-dependence

When two pups experience littermate syndrome, they are so dependent on their sibling for security that they resist anything that takes them out of their comfort zone – meaning any new activity, person, dog, or location.

A Corgi and Terrier puppy playing together outdoors
A pair of puppies sitting in a field

“A pair of closely bonded puppies tend to be ‘in their own world’ and will likely look to one another for how to respond to new stimuli rather than looking to their owner. This gives them the opportunity to feed off of one another’s fear and anxiety, which can develop into unhealthy behaviors.”

– Harmony Diers, Veterinary Technician at the Texas A&M School of Veterinary Medicine and Biomedical Sciences.1

Separation anxiety

The result of this co-dependence can be separation anxiety that occurs whenever something causes the two puppies to be physically separated from each other.

  • The pups can be so overwhelmed by the separation that they could have a complete meltdown.
  • Something as simple as walking on separate leashes can be enough to trigger the pups’ anxiety.
An anxious puppy hiding in a grassy lawn

⚠️ Separation anxiety in dogs can manifest as destructive behaviors like peeing around your house, chewing inappropriate objects – or running away from home. Watch out for these signs if you’re looking to prevent an escape attempt.

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Track Your Runaway Dog

Poor social skills

Even though your two pups are always socializing with each other, that doesn’t mean that they are good at socializing with anyone else.

  • If you’ve raised your pups exclusively together beyond three months of age, they might’ve missed a critical phase of puppy development. Aka, the opportunity to interact with other dogs and humans.
  • Even worse, your two puppies may not have equal status – one may be more dominant than the other, which can lead to aggression.

As a result, your little buddies might not develop to their full potential.

Two puppies playing with a plant together outdoors
A pair of puppies sitting in a field

“Littermate syndrome often causes aggression in breeds that are not prone to aggressive behaviors. For example, we rarely see aggression in Labradors, but when two Labrador littermates are raised together we see much higher levels of aggression and or fear.”

– West Suburban Humane Society2

Training difficulties

As a rule, puppies can begin training as early as 8 weeks old – or as soon as you bring them home for the first time. Training your pup is essential to establishing good behavior and strengthening your bond.

But training even one puppy at a time can be challenging on a good day – let alone two with littermate syndrome!

A woman training a Labradoodle puppy in a garden

In the latter case, dog training gets exponentially harder. Why? Because your dogs are so co-dependent that that struggle to pay attention to anything else.

💡Which is why we recommend you train your puppies separately – maybe get a friend or family member in on the fun. With a practical training method like clicker training, you can help your little buddies pick up “good” behaviors based on positive reinforcement.

Read more: Clicker Training for Dogs: A Step-by-Step Guide to Positive Reinforcement


When two pups are codependent, they may focus so strongly on each other that they fail to interact with the people and things around them. They never develop the confidence that comes from exploring and learning about their surroundings.

The result? A powerful fear of anything new, which sends them directly to their comfort zone with their sibling. And like we’ve covered, a fearful dog is one that’s more likely to run away from home.

Read more: Expert Bettina Specht Reveals Everything You Need To Know About Fear In Dogs

A scared puppy cowering in a corner with an older dog

⚠️ Loud noises like fireworks can majorly trigger your puppies’ noise anxiety and trigger an escape attempt to somewhere “safe.” (Whether that’s a narrow spot in your home – or miles away from safety.)

So make sure to be extra mindful of their whereabous during festivals like New Year’s, Bonfire Night, or the 4th of July.

(Or track them in real-time – with just a glance at your phone.)

A pair of puppies sitting in a field

“Even with a leash, safety harness and training, you can’t be 100% sure that your dog won’t escape. For that reason, a GPS tracker is recommended for dogs who are prone to fear and anxiety attacks.”

– Bettina Specht, Animal Welfare-qualified dog trainer & Nutritionist3

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Sibling aggression

While not always present with littermate syndrome, one of your puppies might be more dominant than the other. (Leading to at least a few squabbles and sibling aggression down the line.) Your dominant puppy’s “bullying” might grow worse with time if you don’t take steps early.

Which, in the long run, might get them in a worse situation if they end up picking a fight with the wrong pet, person, predator, plant, or even pet thief.

Read more: How To Make An Aggressive Dog More Sociable

puppies running through grass

What behaviors might signal littermate syndrome?

The behaviors associated with littermate syndrome can appear in any dog – or in any combination. It’s not always possible to pinpoint the cause of anxiety, aggression, or destructive behavior in a dog, even if it is being raised with a littermate.

Which is why experts recommend you view each of your dogs as an individual – with unique temperaments and personalities. This can help you address their behavior in a more personalized way.

A puppy sleeping in a blanket next to a woman

⚠️ Because in the end, simply blaming littermate syndrome for your dogs’ symptoms might cause you to miss out on other causes for their anxiety or aggression. (Like, say, moving new houses, teething, or even being in heat.)

Does littermate syndrome go away?

The short answer is no, littermate syndrome does not go away on its own. But the good news? You can address the behavioral issues that arise from two sibling puppies being raised together.

With time, effort, and consistency, you can help your puppies socialize properly, develop better skills, and behave better.

You’ve already adopted a pair of littermates?

Raising a pair of sibling puppies does not guarantee that they will develop littermate syndrome. If you’ve already adopted two pups, your first task should be helping each pup be comfortable without their sibling.

This includes training, crating, and walking them separately.

Two puppies exploring a forest together

Yes, this is time consuming, but remember that your goal is to nurture each pup’s self-confidence and to build a strong bond of trust. And to get there, your little buddies need to develop the courage to spend time by themselves and grow into confident young dogs.

Should you rehome one of your puppies?

Sometimes, the aggression that arises from littermate syndrome can lead to unsafe situations, especially for the less-dominant of the sibling puppies. Or, if the two littermates develop a pack mentality, they could team up to be aggressive toward other dogs or people, including you.

When your pets are aggressive, they are not happy, playful, or relaxed – and neither are you. So make sure you address aggressive behaviors as soon as they appear. Your veterinarian or a professional trainer can be a great resource.

A puppy biting into a chew toy in a game of tug of war

If you’ve tried everything possible and nothing is reducing the aggression, it may be time to consider rehoming one of your pups. Your dogs and your family deserve to live in a safe and peaceful environment.

Will a third dog help with littermate syndrome?

Some say that having a third dog – not a puppy, but an older dog – can help avoid littermate syndrome.

In theory, the sibling puppies bond with the older dog as well as each other, which may help them develop better social skills. There is no solid evidence to back up this claim, and of course each situation is unique.

(But it could be worth a shot – especially if you can give a third, older dog a loving forever home.)

Three puppies playing together in a tunnel
A pair of puppies sitting in a field

“It also can be beneficial if the pair of puppies join a home with an older dog because in some cases, the older dog can teach boundaries and offer appropriate corrections when necessary.

Nevertheless, you should always seek the advice of your family veterinarian when deciding on bringing a puppy or two home and gather information on behavioral intervention when necessary.”

– Harmony Diers, Veterinary Technician at the Texas A&M School of Veterinary Medicine and Biomedical Sciences

How to fix littermate syndrome

Overcoming the behavioral issues associated with littermate syndrome is a huge task. If you want your dogs to ultimately become confident when separated from each other and disciplined when they are together, be prepared to invest the time and energy to reach these goals. It will be worth it, we promise!

Address their separation anxiety

The first step in fixing littermate syndrome is to help your sibling puppies get used to being apart from each other. Without this important step, you can’t help each dog individually without one or both of them experiencing a meltdown.

Easing your pups’ separation anxiety is a slow process of desensitizing them to being away from their sibling. Simply placing them in separate rooms and closing the doors won’t solve the problem. This will just create more separation anxiety.

  • Start by buying two crates of the proper size. Place each puppy in a separate crate, but keep the crates right next to each other, allowing the puppies to see, smell, hear, and touch each other.
  • Over the next few weeks, move the crates farther away from each other. Always make sure the puppies can still see each other. Eventually, the puppies should be able to remain calm while on opposite ends of the same room.
A puppy sitting inside a crate outdoors
  • Once the puppies can remain calm for 30 to 60 minutes in their separate crates, try moving them out of sight of each other. You can leave them in the same room, but slide a box or chair between the crates so they can’t make visual contact with each other.
  • During this process, keep a close eye on the pups. If they become overly anxious, whine constantly, or bark constantly, go back a few steps in the process.

💡 One key to success is offering a frozen treat or toy to each pup while they are separated from each other. This will help the pups to equate alone time with positive experiences. They may even begin to look forward to being separated!

woman in green sweater holding small brown dog with cages in the background

⚠️ Just make sure not to keep them in their crates for too long.

In some countries (like Austria), the legal limit is around 20-30 minutes. You could also consider crate alternatives like puppy fences or keeping them in different rooms.

Train your puppies separately

Once your dogs are OK with being apart from one another, you can begin training them separately.

Dog training sessions take a lot of concentration and to make these sessions successful, your dog must be completely focused on you. Having their sibling present or even in the same room can be too distracting completely disrupt your dog training session.

A woman training a puppy in a lawn

⚠️ Obedience training is not a quick process. Be prepared to spend months, if not a year, working on this process. Not only will these training sessions help your dogs learn confidence and independence, you’ll build a bond of trust with each pup.

Build their independent behavior

Now that each puppy can be away from their sibling and has their training basics down pat, you can reinforce their independence by treating each pup as a separate dog – not as a single unit.

Which means you now have to:

  • Feed them separately
  • Take them on separate walks
  • Play with them separately
  • Take them to the vet one at a time

Besides, it’s also a good idea to spend some time separately with each puppy – so they get to bond with you without their sibling around. (Demanding attention instead.) With this kind of quality time together, you’re more likely to help encourage their independence and secure attachment.

Three puppies sitting on a street outdoors

Get them back together

During this process, your dogs will of course see each other and spend time together. But you should only take them out on walks or training together once they’ve gotten used to being happy and relaxed while apart.

Follow our puppy socialization checklist

Socializing your puppies can seem challenging – with all the risks and dangers they can face coming in contact with other pets and people. So here’s a checklist for you to get started with, for each puppy separately:

– Adults
– Kids and babies
– Elderly folks

Pro tip: introduce your puppy to people wearing different types of clothing – like jackets, caps, sunglasses, etc.
– The vet office
– Pet stores
– Boarding and daycare facilities
– The park
– Shopping centers
– Family gatherings (and anywhere else you might bring along pets)
Gentle handling or touchingAnimals
– Ears
– Paws
– Mouth
– Tail
– Collar
– Gentle brushing
– Other puppies
– Adult dogs
– Cats
– Any other animals your puppies might be exposed to
OthersSights & sounds
– Stairs
– Water (especially in a tub)
– Medical equipment (like canes, wheelchairs, crutches)
– Floors and surfaces (tile, wood floors, carpeting, grass, cement, etc.)
– Entering and riding in cars
– Passing vehicles
– Car horns
– Bicycles

How to avoid (or plan ahead for) littermate syndrome – for good

Your life is busy enough without having to help two puppies overcome serious, long-lasting behavioral issues. Rather than get two puppies at the same time, get just one pup, then adopt another puppy a year or two later.

This way, you can focus on raising confident, independent dogs and building a solid bond with each of them.

Because littermate syndrome can come accompanied with harmful symptoms – including fear and separation anxiety. (Which can drive them to run away from safety.)

A puppy gnawing on a tree branch

So plan ahead for these by:

  • Ensuring your puppies are microchipped by 8 weeks. So that they now have a permanent ID tag to help a vet or local animal shelter identify you as the rightful owner.
  • Equipping your puppies with a dog GPS tracker. So you can follow their movements in real-time and over an unlimited range – and never worry about losing them again.
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packaging of the Tractive GPS DOG tracker

Always know where your dog is

Follow every step in real-time with unlimited range. Get alerts if they wander too far. Keep them happy & healthy with Wellness Monitoring. And let others – like walkers or sitters – keep an eye on your dog too.

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Here’s a video that covers littermate syndrome and what to do if you’ve adopted two puppies from the same litter:

And if you’ve liked this post, share it with a friend or loved one – and let’s help build a safer, kinder world for our furry friends together.

Marina Selinger, UX designer at Tractive & licensed dog trainer

This post was written by Marina Selinger, a licensed dog trainer and international agility competitor. Besides putting her UX design skills to use in Tractive’s Product team, she’s also mom to 3 high-energy Shelties and a Japanese Spitz.

When she’s not sharing her expertise for the Tractive blog, you can find her walking her dogs, hiking, or in the middle of a high-speed training session.