I used to have a problem like that. Snickers is my cat and Kuro is given by my uncle. Anyway, at first Snickers does not like him at all and hissed and pounced at Kuro. Kuro is friendly enough, though and try to play with her. After a few weeks of hissing and pouncing and fighting they get along. Snickers will lick Kuro's fur for him because he's too lazy to lick his own fur. And Kuro will play with Snickers because his age is almost the same as SNickers (2 months difference).
@gothfulbunny>Are you talking about me? LOL. It's true. I can't stand children and their noises but I can stand cats and cuddle them everytime eventhough sometimes they can be a pain in the butt.