You did not mention your age. If (your family) is what is keeping you from being with the man you love I suspect you must live at home or be a teenager.
(Adults get to choose their own friends, lovers, and spouse.)
If you are a teenager there may be a good reason why your folks don't want you to get involved with him. As for him having a girlfriend that should be expected. Young people are expected to live life in "the now". This is especially true if they are unable to be with someone. Life goes on. This happens all the time when teens go away to college. The first couple of semesters they make the effort to stay connected to their high school sweethearts. However as time goes by they make new friends on campus, socialize, attend parties, join fraternities or sororities and gradually start becoming involved with people who are actually (available) to be with.
Let go of the Romeo & Juliet idea of romance forbidden by family. You are over romanticizing your situation. You are not each other's soulmates. Your ex has accepted the (reality) that you and him are not going to be together and therefore he has (moved on). You should do the same!
Just because he still likes you or has fond memories of you does not change the fact that he has found someone who is (available) to be with him. You don't want to end up becoming a secret "booty call" or the girl he cheats on his girlfriend with. You will be powerless in all relationships until you are in a position to make your own choices. Eventually most of us move away from our parents.