neutered male mounting

Hi all. I have a female cat, Molly, she'll be two in august. In October i took in my friends cat, Flaco. He seems to be aggressive with molly, he pins her down on her back and tries to bite her stomach/groin. But it's lessenning now that theyre together more.

There was some confusion as to whether Flaco was neutered or not. Numerous people said he was neutered, including the people at the shelter when i brought him to get a free rabies vaccination. (confusion because he sprayed when we first got him).

Last week i got another cat, Taylor. My dad got him from the shelter and since he lives in a studio and the cat is still young he couldn't take his energy, so i offered to take him in. The shelter said he was 2, but my guess is he's a little over a year, maybe 14 months. The shelter neutered him before my dad brought him home, so he was neutered 2 months ago. I've let Taylor out for a couple of minutes a day since sunday. Flaco constantly tries to mount him and wrestles. Is this a dominance thing? Is he just an aggressive cat?

Hmmm, well not sure. I have a brother and sister and Milo play fights with his sister Pepsi all the time and looks as though he may be getting all hot and bothered (so to speak). We have neck biting and general pining her down and rolling. Some times I think they are just playing and other times I am not so sure. They are both neutered. Is Milo dominant or aggressive, I dont think he is either. He sits and lets Pepsi eat first and when she is done he gets up and gets his fill, that sounds like she is dominant, but then I am no expert! Neither of mine has drawn blood and generally seem happy and content, so maybe its just a male thing!!