Why are you trying to avoid becoming a womaniser? It's a good thing, you should embrace it. Become like Charlie Harper. Your brother isn't doing anything wrong or bad. It's not considered cheating if you're not married, just because you have a girlfriend doesn't mean you can't have sex with other women. If she doesn't like it or accept it then break up, very simple. You can still treat them well at the same time, it's fine.