It would probably be helpful for you to read a book on Alcoholism. And given that you are an adult child of an alcoholic, I'm willing to bet you'd benefit from AlAnon.
I truly believe that specific types of people come into our lives so that we can learn the next thing we need to learn in order to continue to grow. The fact that your mother and brothers are alcoholics speaks volumes to me. There is a reason you are attracted to and interested in this guy.
"The search is what any man would undertake if he were not sunk into the everydayness of his own life. To become aware of the search is to be onto something. Not to be onto something is to be in despair." Walker Percy