ArtFriend,
maybe some counselling around boundary-setting would help? that way, you might be able to be more assertive without having to banish your brothers entirely...a lot of community centres and nightschools have short courses in this, too.
as far as your own internal logic for your drinking - i doubt it's too terribly individual. probably much like most AV-stuff, only slightly personalized for just your circumstance. BS none-the-less
