Both of my cats are quite happy sharing...but with only each other! Every time Ive had more than Remus and Spook in the house they've become rather teritorial (fur flying terirorial ) They are about six months apart, and I guess I just got lucky that they tolerate each other so well! I think having siblings will help, as they are used to sharing accomodations as is.

Im looking forward to "meeting" your pair