I think it's more environmental than anything. My grandpa (mom's dad) was an alcoholic, and took him two strokes to decide to quit.
My mom's always been an alcoholic, and still is. She tried to quit once when we moved to Texas, but it only lasted about a month. Back in the day, she was in charge of the beer cart / cooler for the local softball team, was manager of the golf course club house (ie. drinking place), and was even manager of a liquor store for a while. The last one she thought was great, because she got beer at bulk rate.
Have two older brothers, 7 and 3.5 years older. I grew up in a small oil patch town, and drinking is simply what you did, and what everyone did. My oldest brother was a bit of a devil in his teenage years (ie. drug dealer, thief, etc.). Dad was never really around, because he was always out of town at camp working to support the family.
So when my oldest brother was 16/17, I was 9/10, and that's when he began throwing huge parties at the house all the time. And not exactly the healthy kind of parties. The kind where you watch your mom get punched in the face by some guy stoned out of his mind on cocaine, or watch people get carried inside unconscious with blood all over because they were in a fight over $5 in beer money, or where the cops show up every weekend, etc.
This was my life for years starting at age 8/9. My oldest brother was the worst, but once he was out of the house, my other older brother started up with the parties at our house. They were more tame than previously though, so not as bad. My mom actually encouraged the parties, because then she had people to drink with, and again, my dad was out of town working.
By the time both of my brothers were out of the house and off to college, I finally began normalizing. I was actually getting in with a great crowd of friends (the "coolest group in town", kinda thing), and things were going really well for me. Then a few months later I got moved to Texas.