There's this guy who I've been friends with since high school. He has a girlfriend (who he never talks about and is never around) plus he used to date one of my friends a few years back. However, he likes me. We hang out and he's even kissed me. I enjoy hanging out with him but I only like him as a friend. I also don't want to hurt my friend nor interfere with the relationship he has with his girlfriend, yet, I don't want to lose him as a friend either. What do I do?

For one thing you don't let him kiss you
Tell him you only like him as a friend. There needs to be boundaries
In fact the wise thing would be to leave him alone. If he has a girlfriend and likes you, you are already interfering by hanging out with him.