You know, i don't think this question applies to many desis. I have seen many people marry their friends sister. It's a way to get closer to your friend- atleast with in the desi cultue that I come from.
What normally happens is is that if you like your friend's sibling you ask the friend if their sibling would be okay with marrying him/her.....The friend basically becomes a mediator....
I actually never understood this rule in American culture (And I'm an ABCD)- there are just too many rules about dating- can't date friend's sibling, your friend's ex, don't marry cousing (that I can undersand, but to make a point) making the pool of eligible good guys smaller and smaller till no one's left....
DISCLAIMER::::Just my personal observational experience- Please nobody shoot me down for making immature generalizations....please.... I think I'm going to start adding this disclaimer to each of my posts because I don't know how many of you have noticed but there have been alot of "gang fights" on GS going on recently....I have to think 10X before I write something, and it's sucking out the fun.
I think I'm going to add that too....i got shot down on my very first post :(