It depends on how much he likes his girlfriend. The guy can not like his girlfriend at all, thus he will like another girl.
If you like a guy and he has a girlfriend then you should back off and only try and be his friend.
wait
...
you use his girlfriend like a ladder and jump over him
tell him u are willing to be the girl on the side. But really if the guy has a girlfriend already why not try and like some one else.
He has a girlfriend. So you butt out. It's not complicated.
If he has a girlfriend then he may like you but not as much as his girlfriend. You need to tell him you cannot go out with him while he is still with his girlfriend as it is not fair on you or her.
You try to get his attenion. try to make him feel like you are better than his girlfriend.
You simply ask him.
you can tell him, or his girlfriend if you are friends with her
Yes.