It is perfectly fine to have seperate groups of friends, and for many good reasons. For example, I have a friend who is a strict Roman Catholic and won't talk about anything except education and his Catholicism. I know for a fact that if I tried to invite this friend to hang out with my other friends, most of whom are either non-Catholic Christians or non-Christian, he would either blurt out something about how they are wrong about their beliefs or sit there with a fake half-smile, arms crossed over his chest, and ignore them. (BTW, this Catholic friend is also an Aspie, which would go to explain his complete lack of tact). I think some of my friends would not mix well with other friends, so I don't try too hard to mix "friend groups".
_________________
It's an Aspie thing: Don't even TRY to understand!!