I don't know, if some guy asked my brother if he could take me out (especially before asking me) I'd be pretty insulted. I'm an adult and regardless of said guy's relationship to my brother I'm quite capable of deciding for myself who I want to date. This isn't the 18th century...we actually have the right to vote, work outside the home, and live in our own apartments, certainly we're also capable of dating (or not) who we choose.
Cindie