My parents have 2 cats, same mom, different litters. They fight, with the male getting the best of the female. (Sister is very shy, slender and skittish, brother is just a big 25# bully but loves the attention.) My mom would put him in the basement for awhile, like an hour or so, then let him back up. Whenever he entaginized his sister, basement for him. It's decreased this behavior but he still tries to get away with it...