My father drank every night probably as a result I've never drank with my parents or in their house. So they would have no idea.
When I tell my wife that I'm quitting she says she'll believe it when she sees it. But she has never complained about my drinking. I'm more of a binge drinker so she'll complain about me being sick or making a mess. Drinking has never resulting in me letting my family down through being hungover or drunk though. My wife probably just thinks I like alcohol. Her family history has no alcoholism as far as I can see as she can't (she's Japanese) stomach alcohol herself. Basically she's wouldn't have the experience to know.
Personally I noticed it for myself. I began to stop having a good time when drunk. Then once I was told to leave a bar as I was annoying other customers. I was mortified and then shocked when I felt I hadn't done much wrong. This incident led to introspection and then to this site. The more I read the more I could see glimpses of myself. With this and my family history (both sides) of alcoholism I decided to stop before it became inevitably worse.
Still don't know where I stand. Once I get by the first Saturday night I am generally ok-ish. When drinking I don't have the will power to resist and when not drinking my will power is super strong.