Oh Brother Where Art There (2000) - I didn't like this movie when I first saw it, but my husband loves it, and it grows on you. There really are some funny moments, and George Clooney isn't hard to look at. Technically, it's not about brothers, but it was directed by the Coen brothers. Set in the South during the 1930's, it's about three escaped convicts who are on a wild-goose chase for some hidden treasure.
Legends of the Fall (1994) - This is a great movie! In fact, I think I want to re-watch it this weekend. This one is actually about brothers, although Brad Pitt isn't hard to look at, either! It's also set in the early 1900's, but this time in the wilderness of Montana. It explores the bonds between brothers, love, relationships, trust, betrayal. Anthony Hopkins also stars.
Rain Man (1988) - Definitely about brothers - totally opposite brothers. Tom Cruise and Dustin Hoffman put in great performances. When his father dies, Charlie (Cruise) finds out he has a brother to whom his father left his fortune. It turns out, the brother, Raymond, is an autistic savant who has been living in an institution. Charlie kidnaps Raymond and takes him on a cross-country adventure. Great movie!
Well, I gotta go. It's "Four minutes till Wapner!"