Hi Andrea, I think you may get conflicting advice wherever you ask this question.
Chipmunks have such different personalities knowing which chippies will get on with which is impossible to guarantee. Brothers and sisters can all fall out with each other as they mature.
What I think can help minimise having to separate them later is as DayleC suggests get siblings from the same litter. Move them together into a brand new aviary (as you are doing). It will need to have plenty of space, with lots of places for the chippies to hide from each other if a fight breaks out.
It may also help to put out two lots of food, instead of just one to reduce squabbling of who has first go at the food bowl.
Try to get them from a breeder rather than a shop, because shops have often been known to make mistakes over the sex of the chippie, and probably may not know for sure if they are all brothers.
Even the most happiest of groups will have the odd light squabble, as they sort out or test who is where in the pecking order.
Good luck with whatever you decide to do.
