I think the genetic aspect is a theory, amongst others but maybe I'm wrong.
My dad was an alcoholic. My mum's dad was an alcoholic so she married an alcoholic and enabled him as her mum enabled her alcoholic.
My siblings are alcoholics/heavy drinkers as they were brought up with an alcoholic and that was the behaviour modelled. Very heavy drinking was the norm for us and we were brought up with all the chaos that alcoholism brings and co dependence brings.
I used to binge drink and I think I'm allergic to alcohol (there's also a theory that alcoholics are allergic). I don't drink as much as my siblings though, my sister can drink three bottles of wine. I would be sick after one.
I think it's a lot of different factors OP. My younger sister drinks because of the trauma we suffered as children. She was hiding bottles of wine in her cupboard from the age of 15. She's a very heavy drinker now and always has been.
I was brought up the same way and I haven't drunk in a year but I'm also aware that I have co dependency issues and have got into relationships with people with other addictions such as workaholism for example. What I mean is, that addiction is not just about booze. It can take any form like workaholism or sex addiction or drugs or relationships or food. Just because you don't drink, doesn't mean you've beaten it.
It takes a lot of work, in my opinion, to get over the complex mess an alcoholic parent leaves in their wake.