Wayne, this is something I've never heard before but it could be true. You can carress Tigris' paws and he is the much more social cat. And you can carress Filou's paws from time to time but not always.
Regarding the fighting cats I must agree to Wayne: you cannot be sure that they will ever be friends. But in general they find ways to divide the apartment so that they can get along. You should make sure every cat has a place of her own.
My 2 are in between: Although they know each other since they were 3 months old they fight a lot. In general Filou (7lb) attacks Tigris (13 lb) first and makes a drama out of it, but I am also afraid, Tigris could hurt him. In general it's just hair and no blood and there are times where they clean each other and sleep together.