It's commonly known as late onset alcoholism. Personally, I almost never drank before I was about 30 (20 beers a year?) and used alcohol in a "normal" way for about 10 years, before being sucked into 10 years of heavy abuse.
I had lost my dad to alcohol when I was 13, so it was never going to happen to me...err... right. To be fair, I was a very responsible kid, never got drunk, even in college. What happened to my dad played a big role in that. And yet...
I don't think it matters much when it comes to the nature of our addiction, and to the solution, which for me (and I think for every alcoholic) was complete abstinence.
I was always able to have fun as a youngster without alcohol. It simply didn't play a role. And that image, that idea, that feeling made it easier for me to imagine a life without the stuff again. I guess I'm saying you can use it as an advantage?