Psychologically Genetic

Now, I completely understand that this is probably not a real scientific or medical term. Forget about trying to prove to me why it can't be possible. I get that. But the phrase makes sense to me...and really, in MY blog, that's all that matters.

Follow me here:
I have an older brother. He is an alcoholic. His biological father was an alcoholic. My brother only lived with his biological father for a couple of years, maybe three. There is alcoholism in our mother's family; her brother and father. Although we did not grow up in a home of alcoholism, we were occasionally exposed to the behavior.

I believe alcoholism, or the tendency for it, is hereditary. I understand that children of alcoholics are pre-disposed to the disease. All of that makes sense to me.

But here are my questions:

*If someone came from alcoholism, but didn't know it (maybe they were adopted), and was raised in a home without alcoholism, what are that odds that they would become an alcoholic?
*If someone KNOWS they come from a history of alcoholism, are the odds more in favor of them becoming an alcoholic, even if they weren't exposed to it on a regular basis? And if the odds are higher, wouldn't that be psychologically genetic? "I come from an alcoholic, so I must be doomed to be one."
*What's the difference between the children, from the same parents, who become alcoholics and those that don't? How is my mother not an alcoholic, but her brother was? How is my biological father not an alcoholic, but both of his brothers are?
*I understand that someone can become an alcoholic because of psycological reasons. What are the odds that someone who didn't come from alcoholism becomes an alcoholic?

The statistics don't matter, in the big picture, because I still believe that no matter what genes we have, alcoholic or not, we are each still responsible for our own behavior. And it drives me crazy when alcoholism is used as a crutch and an excuse for stupid behavior.
There, I said it.