Keeping siblings from a litter seems like a good idea. The dogs already know each other, and by having each other they won't get bored or lonely while you are away. Raising siblings can create its own set of problems, though. If you do have dog siblings, there are some things you can do to curtail behavior issues that crop up as a result of raising littermates together.
Keep things separate. Your pups needs to have separate crates and food dishes. There needs to be separation between these items as well; keep the crates in different rooms if possible.
Spend one-on-one time with each dog, every day. If everything is a group activity, your dogs will maintain their dependent relationship with each other, and not really bond with you. This is not healthy, and can lead to problems with the dogs not being able to be separated, ignoring or being aggressive toward you, or even fighting with each other, because they never matured mentally.
Socialize the dogs. It is tempting to think that your two dogs have each other and you and don't need additional socialization. They, like any other dog, need to learn how to be around other dogs and people. Take them out separately for walks, to obedience classes and to dog parks so they grow into well-adjusted dogs.
Allow them to play together. You don't have to keep the dogs separated all the time. When they are spending time together, make sure you stay involved. For example, if they are playing in the living room, randomly call them into the kitchen. They should stop what they are doing and come to you. If they ignore you and continue to play, it may be time to interrupt with some obedience work for one dog while the other goes outside for a while.