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Understanding Littermate Syndrome: The Challenges of Raising Sibling Puppies

Before you get bamboozled by two sets of super cute puppy eyes or fall for the "they are inseparable siblings" trick, there are some things to know about raising sibling puppies that could save you headaches and heartache down the road. 

Understanding Littermate Syndrome: The Challenges of Raising Sibling Puppies

Before you get bamboozled by two sets of super cute puppy eyes or fall for the "they are inseparable siblings" trick, there are some things to know about raising sibling puppies that could save you headaches and heartache down the road. 

By: Sara Ondrako, Certified Canine Behavior Consultant

What could be better than bringing one bundle of fluffy joy into your home? Perhaps two fluffy bundles of joy! Before you get bamboozled by two sets of super cute puppy eyes or fall for the "they are inseparable siblings" trick, there are some things to know about raising sibling puppies that could save you headaches and heartache down the road. 

Separation-related problems, training difficulties, attachment issues, aggression, and other behavioral and emotional challenges can arise from raising two puppies simultaneously - even if they aren't littermates. So, let's talk about what littermate syndrome is, how it affects more than just littermate siblings, and strategies to prevent and address it.

Two Golden Retriever puppy littermates run through a field

What is Littermate Syndrome?

Littermate syndrome is the term used to describe various troublesome behaviors that arise with the challenges of raising sibling dogs together. Here, "siblings" means two puppies from the same litter or of similar age that are acquired at the same time (even if they are from different litters). Though the term implies a relation, the puppies do not have to be related. 

The phrase "littermate syndrome" is often not recognized by veterinary behaviorists or behavior professionals because the subsequent behaviors and emotional concerns relate to how puppies are raised together, not their genetic makeup or innate personality. Littermate syndrome is not regarded as a phenomenon that will inevitably occur between littermates but rather the product of challenges with meeting the individual needs of two young puppies at once. 

Causes and Factors Contributing to Littermate Syndrome

During the period of a puppy's life before twelve weeks of age, critical factors are at play that determine how puppies will respond when being raised together. These factors include individual personality, influence of the mother dog, social exposure, relationship with the humans in the home, and the age at which the puppies are separated from Mom and other littermates.

Once your new puppies come home, environmental factors also enter the mix, which can ultimately contribute to the development of littermate syndrome. These factors include:

  • The puppies spend all of their time together with inadequate independent time.
  • One puppy over-relies on the other puppy or an older dog in the household.
  • Pet parents do not spend enough one-on-one time with each puppy individually.
  • Pet parents provide inadequate individual training sessions before attempting to train the puppies together.
  • Not enough social exposure and interaction with other people, animals, and situations leads the puppies to rely on each other for socialization.
  • Poor timing with reinforcement (treats and praise) while training, leading to confusing communication when trying to train two puppies at once.
  • Pet parents do not have enough time to meet each puppy's individual needs and work with them together.

Siberian Husky littermate puppies playing

Behavioral and Emotional Challenges Faced by Littermates

Raising one puppy is a significant time commitment, so it's understandable that pet parents of two puppies can have an even harder time teaching their new furry family members everything from potty training to verbal cues. This can lead to frustration and inconsistent training, and dogs are much more in tune with our body language than we give them credit for. When a pet parent is frustrated or stressed during training, puppies can respond with mischievous or challenging behaviors. And once one puppy gets started, the other will likely feed off of their energy another, making the situation worse. 


When siblings are kept together without proper intervention and training, they may become overly dependent on each other, hindering their individual growth and social development. A lack of independence can impede their ability to function confidently when their sibling is absent, leading to separation anxiety

Sibling Rivalry

Competition for resources like food, attention, and territory can lead to aggression and stress, contributing to behavior problems and fights.


Siblings sway each other into or out of something, including mischievousness. Their behaviors and even emotional states can be influenced by each other, causing them to respond to things differently than they otherwise might. For example, one puppy may chew a shoe while the other chews a toy. In this case, even the puppy chewing the toy may nibble on a shoe in the future because he saw his sibling chewing a non-toy item.

Destructive Behavior

Destructive behavior is more than just typical puppy teething or biting and can be more common in sibling pups. Destructive chewing is tied to a lack of training. It often involves tearing things apart due to stress or trying to get out of a room or home, leading to broken objects or even injury to themselves. This can be caused by several things, such as hyper-attachment, being overwhelmed by the littermate, or even not getting enough time with their human family for training, play, and exercise. 

Growth and Development Issues

When littermates or puppies of the opposite sex are brought home together, spaying or neutering may be required at an earlier age than typically recommended for physical and hormonal growth and development. This is to prevent unwanted litters and irresponsible breeding of puppies not yet mature enough to raise their own puppies.

Puppies become capable of reproduction as early as six months of age and can conceive very quickly. Neutering before six months can prevent pregnancies, but most recent research shows that some breeds, when neutered early, are at a higher risk for developing joint disorders, cancer, and urinary incontinence. 

Black and white littermate puppies

How to Prevent Littermate Syndrome in Dogs

If you've decided that you're ready to raise two pups at the same time, here are some helpful tips to prevent problematic behaviors associated with littermate syndrome.

Early Prevention Strategies

Step one to preventing littermate syndrome is to be prepared. Have things set up beforehand, such as where the (separate) crates will be in the house and where the dog beds are. Get two sets of everything, like collars, leashes, and food bowls. Consider working with a dog walker or caretaker to help schedule appointments with your veterinarian, and make sure you've booked your puppy training classes well in advance. Once you've ticked off all the items on your new puppy checklist, you'll be ready to bring home your new bundles of joy.

We also recommend staggering your new puppies' welcome home parties. Each dog needs time to bond with you and settle into a routine the first time you bring them home. Whether you are working with a rescue or a breeder, bring home one puppy at a time with at least a two-week gap between arrivals. This can help you get through the honeymoon period with puppy number one and develop the foundation of their daily routine to make it easier to focus on puppy number two when you bring them home. Starting with one puppy can also help you form a bond with puppy number one so that it is easier, in the long run, to create individual bonds with both puppies. 


Be ready for three times the work! Puppies are hard work on their own, and pet parents often make the mistake of thinking they will train two puppies at once. This can be incredibly challenging with one fast-moving puppy brain and body, never mind two! Timing in training is critical, whether it's the timing in marking and reinforcing behaviors you want your puppy to repeat or being quick to interrupt and redirect unwanted behaviors.

Individual attention and training are needed to effectively communicate with your puppies. Plan on three short training sessions every day with your puppies separately. As they get better with their cues individually, you can start bringing them together to try simple cues and training exercises simultaneously. 

When possible, tether one puppy to one person for expedited learning and connection between puppy and pet parent. Tethering one puppy to one person with a hands-free leash can also help speed up potty training and keep puppies from being a bad influence on one another when they slip out of sight momentarily. 

Don't skip the puppy training classes or think you can teach what one puppy learns in class to the one who stayed home. Part of the benefit of group puppy classes is social exposure, which is a critical part of puppy development. Puppies respond differently to training in different environments. Having one handler per puppy per class allows you to work through each puppy's challenges and celebrate achievements together. This, in turn, strengthens your relationship and builds a better bond.

Remember that dog training isn't a one-time event during puppyhood and isn't just about basic obedience training. Dog training lasts for the dog's lifetime to prevent behavioral issues and set them up for success as they grow and develop well-rounded social skills and good behavior from puppyhood through seniorhood. 


While you may be tempted to toss your puppies into a puppy playgroup or let them play together for socialization, proper socialization isn't just about playtime with another pup or a group of dogs. It's about exposure to new smells, sounds, sights, and experiences while learning to respond to those stimuli with your guidance. 

Socialization does not necessarily mean physical contact. While puppy playgroups are fun to burn off some energy, they do not provide enough socialization to develop well-rounded, socially stable older dogs. Take the time to visit new places, explore new smells, and observe new people and animals of all ages with each puppy separately so they can learn in their own way. It's perfectly fine to take them together, too - just make sure they get that essential individual social exposure as well!

Set a Schedule for Success

Choose activities to do with your puppies that match the natural ebbs and flows of their energy levels. When you've got double trouble, their youthful energy can promote learning or frustration, depending on how it's tapped into and when.

All puppies require one-on-one time, independent time, mental enrichment, and physical activity that involves the brain. When your puppies first wake up, and their energy level is about to peak, that's the ideal time to be ready for play, followed by physical activity that involves the brain. Once they've got those puppy wiggles out, they'll be primed for learning. After some training, it's an ideal time for some independent time with enrichment as they wind down and prepare for their next rest period.

Build Independence

One of the most challenging aspects of littermate syndrome is separation anxiety, which can occur if the puppies are used to spending all of their time together. Separation anxiety is specific to one person or animal. It involves stress - often to the point of destruction or injury - when separated from the person or animal they are most attached to. To combat this, gradually build up the time the puppies spend separated from one another to increase their confidence in participating. 

Consider incorporating something fun or exciting into your puppies' individual crate times to help boost their confidence when alone. Give your puppies a long-lasting chew or frozen Kong in their crates to enjoy while in their crates or separate rooms. Additionally, one-on-one training, playing, or walking sessions can help them learn they can have fun and be safe when their sibling is absent. While they don't need to be separated all the time, aim to separate them at least once daily for a rest period in the crate.

Three Important Mistakes to Avoid

Avoid thinking you will never separate them. The unexpected can sneak up on you. For example, one dog may require surgery or hospitalization and have to be separated from their sibling, which, if not conditioned, can cause extreme stress for both of them.

Avoid becoming complacent with your training sessions. Until sexual and social maturity, which generally finalizes around two years, genetics hasn't necessarily finished showing us all there is to the hardwired portions of our pup's personalities. Just because there have been no signs of dog aggression, cat aggression, stranger danger, or other surprising behaviors doesn't mean they won't surface before your dog matures.

Avoid overestimating how much time you can commit to getting your dog(s) acclimated to their new environment. Littermate syndrome can occur in many scenarios, including when a new dog is brought into the home to keep an older dog company or two adult dogs are adopted simultaneously. Be ready to make the time to provide for both dogs, no matter their age, to support them through the transition and training. If you need more time to train and provide for two puppies, consider bringing a second dog home only after the first one is fully trained.

Seeking Professional Help

A professional trainer is your best tool for navigating puppyhood, especially when it comes to two at once. Locate a positive reinforcement-based and accredited dog trainer through organizations like the CCPDT and the IAABC. 

If you are already in a situation where you are seeing signs or symptoms of littermate syndrome, it's time to bring a certified behavior professional on board; more advanced behavioral concerns require more advanced skills to tackle. 

While raising sibling puppies can be a rewarding experience, it also comes with unique challenges that must be proactively managed. Understanding the causes and signs of littermate syndrome and taking steps to prevent and address it can lead to healthier, more well-adjusted dogs. By prioritizing individual training, socialization, and independence-building, dog owners can set their furry companions up as best possible to grow up confident, well-behaved adults capable of thriving in various environments.

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