My FI's sister will also be standing up for him as his "best" person. We're trying not to label it as I am also have a man of honor, but when people ask we say "man of honor" and "best woman".
I was the Best Woman in my friend's wedding in Ireland. According to the former Manners Columnist at the London Times, this is the proper term but if you really hate it, you can always call the BM "Groom's Honor Attendant" and your MOH "Bride's Honor Attendant."
I've been calling my FI's sister a groomsmaid and my brother a Bridesman. We haven't worked out actual titles yet (or even what they're wearing).
Have any of you seen that picture on Pinterest of a bunch of groomsmen in their suits, and then a girl wearing a snazzy skirt suit with suspenders that matches what the groomsmen are wearing? We're thinking about doing that....
I'm in the same situation. Informally we refer to them as my Dude of Honor, and his Best Chick. When It comes time to write the ceremony programs I think it will end up being "Man of Honor" and "Best Woman"
Re: Best Woman?
May 2013 February Siggy: Invitations