It has four members; Pete Wentz, Patrick Stump, Joe Trohman and Andy Hurley.
For those of you who think Fall Out Boy are emo posers; they aren't. They aren't even emo, and, like I said, had a life before MTV. It's MTV that made them so popular, along with some air headed teenage girls, who only listen to them because 'PeTe Iz SoOoOoO hAwT!!!!!11'.
Oh, and by the way, there is no 'Tom' in Fall Out Boy. On the From Under The Cork Tree album, some tracks were mixed by Tom Lord-Alge, which could be the cause of this misconception of the invisible 'Tom'.
Normal person : Air is leaking out.