So you have decided on pulling the trigger for one puppy…so all of a sudden the idea pops into your head to get a second. I mean, after all, if you are going through all the trouble of housebreaking and training one…you might as well get a second. WRONG!
It is important to know that knowledgeable and reputable breeders will highly discourage and may not even allow picking two pups from the same litter — or getting a second puppy within a certain time period of the first. However, it does not seem all that uncommon for the average pet owner to somehow get talked into taking two home. My advice: don’t do it. This is one of the major problems with purchasing a puppy from a breeder who just does not hold the knowledge or credentials they need when it comes to the developmental stages of puppies and dogs.
Littermate Syndrome
Littermate Syndrome is also known as Sibling Aggression or Littermate Aggression. In a nutshell, it refers to a whole list of behavioral challenges that tend to present when siblings or two dogs of similar ages are raised in the same household beyond the normal 8 to 10 weeks of age. Whether you get two puppies or not, you should educate yourself with the term littermate syndrome. Two puppies from the same litter living together may develop such a strong bond to each other that it interferes with their ability to interact in a normal manner with other people, other dogs, or any situation where they are not together. And my experience: this is 100% spot on. It always seems you have the introvert that never reaches its true potential, and the extrovert who overshadows the other dog — regardless of how you look at it, the developmental stages are disturbed.
Unless someone is a professional trainer (or along the lines) and has vast amounts of knowledge about dog behavior, I would be against bringing home two puppies around the same age, let alone two from the same litter. To be honest, I do not even like when someone suggests “getting a second dog for their first dog.” A dog should be something you get for yourself or your family — and everyone should be in agreement so the dog has the best chance of success. Adding a second always runs the risk of changing the dynamic and things are not always what one assumes they will be.
In addition to two puppies being double the trouble of expenses, training, and household management, puppies’ brains continue developing until they hit sexual maturity (and even a bit beyond that), and there’s some convincing research that bringing two puppies home at the same time prevents one, or both, of the puppies from reaching his or her full potential.
When a guide dog organization did an experiment and placed two capable puppies in the same raiser household they found it seemed to always cause at least one puppy to become temporarily unsuitable for work — even though both were strong candidates to begin with.
When two puppies are placed together, they learn to rely on each other. One of the puppies always becomes shy, even when both puppies started off as bold and outgoing. This is a HUGE problem, since it means that the shy puppy never reaches his or her potential.
Other abhorrent and heart-breaking effects of Littermate Syndrome:
The shy puppy becomes increasingly withdrawn and introverted and never reaches potential
Often even the “bold” puppy turns out to be quite nervous and uncertain when separated
The puppies often become incredibly co-dependent, exhibiting high anxiety when separated
They often fail to bond to their human family as strongly as they otherwise would, if at all.
At social maturity, these puppies may begin fighting with one another, often quite severely.
Even non-sibling puppies can exhibit Littermate Syndrome when placed together.
Professional trainers recommend against getting two puppies within six months of one another, because the risks are just too high. This doesn’t even take into account the other practical considerations, such as the increased costs of vet care, food, supplies, and training; the extra work of training and caring for two dogs; or the time requirements of two active puppies.
Can littermate syndrome be prevented?
Theoretically, yes, however it’s so difficult as to be nearly impossible in practice.
At a bare minimum, the two puppies would need to be crated and cared for separately, including separate walks, training classes, and playtime with their owners. The puppies need to have more one-on-one time with their new owners than they have with each other, effectively doubling the work and negating any of the possible benefits (i.e. companionship) that they were adopted together for in the first place.
Bottom Line: we absolutely know that puppies do best when brought home separately. If you want multiple dogs, consider purchasing or adopting adult dogs who are already done developing instead.
Source credit: https://k9behavioralservices.com/littermate-syndrome/