He *might* have had some sort of hollow world connection at first, but chances are that he has already turned them into Arrancar.
I really hope there isn't anyone "above" Aizen... he is one of the best evil overlords I've ever seen, and if anyone is pulling his strings it will do nothing but cheapen his character.
I mean come on... His plan is to
Kill God and take his place... that isn't the sort of person that takes orders from anyone.
