I wonder if when they are littermates, that they get along better and without battles? I have NEVER seen my son's twin girls fight, and no evidence of it when no one is at home either, and they are about 8 years old. Pepper only hisses and growls at people - she hates everyone except for my DIL - and she will tolerate me only at feeding time.

When I had my 3 Meezers (not related), they always got along together and never had battles either.