i dont know a ton about dog behavior but i do know some and i have been around a lot of dogs. i think that it is VERY important to socialize each pup seperatly. so that they not only get along with each other but also outher dogs as well. dog parks and puppy play groups are great for this! also, dont let them do everything together, the classes apart will be good for them. being that they are only four months old, i know you dont wanna think about this but there will be a time when one passes on so you want the other to still be able to go on without its sibling. i know that owning two pups is difficult (raising my one was hard enough!), be prepared for them to team up and take on a "pack" mentality. good luck!! enjoy them!