How do you tell your best friend who is in love with someone else.... your madly in love with them??

tell him straight up, or bring up in a conversation if he shows that "i could give a rats ass" type of attitude then drop him and move on because the more you think about him when you know he doesn't care the harder it will probably be on you

Ever seen "My Best Friends Wedding"? Yeah, if he REALLY loves this someone else and is in a relationship with them, I wouldn't say a word. It may completely mess up your friendship. If they break up then fair game. But prepare yourself. If he doesn't feel the same your friendship may take a blow.