[aephi alum]

I don't know enough about the Mormons to answer the question about postponing missionary service. But I suspect most fraternities would be hesitant to pledge someone who's immediately going to disappear for the next two years. (Please forgive my lane swerve.)

I'll say this, though, in regards to alcohol. There's a fraternity at my school that, back when I was an active in my sorority, pledged a recovering alcoholic. Not only did they accept him into their brotherhood - but every semester, the fraternity held at least one dry party, so that he (and anyone else on campus who had chosen not to drink - back in the day most parties were open) could have fun without any pressure to drink. At other parties, his brothers looked out for him. Now that's brotherhood.