Do My Kitties Really Hate Each Other?

I live with my boyfriend and each of us brought a cat into the relationship. His cat, Smoke, is almost 14 and my cat, Topaz is almost 6. I figure it's the difference in age that makes them not get along very well. I also figure that since one is a boy and the other is a girl, there might be some antagonism there. Smoke is the more mellow of the two. I'm not sure if that's because of his advanced age or because his breed is a mellow one in general. When Topaz is around, he's not bothered either way. On the other hand, when Topaz sees Smoke, she immediately hisses at him and runs away. If he tries to eat at the same time that she does, she'll hiss and just let him have the food. Occasionally, I do hear sounds of yowling and see fur flying. They're like a step-brother and step-sister that just really don't get along. I think that Smoke would love her if she let him, but Topaz ain't havin' it!