Family situations are tough, and exacerbated by alcoholism at a high level in my opinion. That said, I don't agree that family of origin takes a back seat to the new family. What I do agree with is that the new family is as important as the family of origin. Not more, but not less.
And, regardless, it's up to him to manage his relationships with both, as it is up to you to do the same. What he doesn't get to do is project onto you what you should or have to do in regards to his FOO.
Their rights/importance ends where your rights/importance begins. If that balance is out of scale it is a problem, but I'm not sure how to solve it. My wife has left me alone to deal with her crazy-ass family and stays out of it for the most part (as do I which is why I get along with them most of the time). As for my family, they love wife as much as I do I think. No problems there thank God. Mom/5 Sisters/Wife/Daughter are very, very close. Too close dang it!
Cyranoak