What ever you want to. if he's a play boy, you might get with him, he might dump her soon, and might get with you. But if he's not, and has been true so far, then their relationship might last a while. Just hope for the best. If you are sort-of-friends, then ask for his number. If your parents know his, then they might organise a day where you two can catch up. Just start up a simple conversation, even though he has a girlfriend. Become friends. Then you're closer. If they do break up, then you will have a better chance at getting with him. Just hope for the best xx