Recently, I had an email question that I thought would be helpful for others to read that answer to. 

"I am writing to inquire it be ideal to train two young pups as service dogs together. There are two members of my family who could each benefit one. The breeder/trainer/rescue involved suggested we wait to get a second pup, rather than taking two home at once."
I am in agreement with the breeder/trainer/rescue.
Firstly, two pups together can be a crazy-making situation! With any pup, the socialization with other people, dogs and environments is key. Toting two growing pups and their equipment around is more than double the workload of one, especially if there is only one person able to do the training! If one or both of you have disabilities, that adds too much on top of the already challenging situation you are dealing with. 

Secondly, having two pups close together in age can create problems with bonding issues with their people unless there is a significant effort to train separately. Typically it’s called “littermate syndrome” where they get so bonded that the humans get squeezed out of the equation. Separation anxiety from the other dog, as well as not being able to train without the other dog present, or relying on the other dog for guidance are all common issues seen. I myself always have gotten dogs that were about 14-18 mos apart. By that time the older dog has a strong bond with their person or people and the pup sees that and usually chooses to bond with the other person. It also helps you to choose a temperament that suits the first dog so they get along. For example, Jessie was very careful about the dogs she plays with and Lucy is perfect in that she always gives Jessie the space and time she needs and goes out of her way to avoid conflict. 

Thirdly, If you or your family member get sick or are unable to continue the socialization during critical periods or can't afford to hire someone else to continue the process, then you have only one dog to do catch up with, not two. 

There are other benefits as well. Once you have learned to train the first dog, training the second one comes easier and the handler/family makes fewer mistakes so general training tends to go faster. Of course, each dog has their own challenges. You learn how to create and what daily structure/environment works for all of you. Puppies tend to fit into those quickly when there are older dogs in the house.The older dog often models the behaviors you want the puppy to do as well (assuming he doesn’t have too many unwanted behaviors. LOL!)

So there are many valid reasons to wait to get the second service dog candidate pup!