The Godfather to Rain Man to The Royal Tenenbaums. The films that took the specific dramatic substance of fraternal relationships as their primary subject.
Brother relationships are one of cinema's most-productive dramatic categories. The structural reason: brothers share a foundational childhood the films can invoke without explaining, while pursuing adult lives that often diverge sharply. The combination of shared origin and divergent adulthood produces dramatic tension that the films can develop without lengthy backstory.
Our picks.
The brother film typically structures its drama around a specific dynamic: one brother who has succeeded by the social standards both grew up with, and one who has not. Michael and Fredo. The Tenenbaum siblings (each one a former prodigy now adult-failed in their own way). The Fighter's Ward and Eklund. Warrior's Conlon brothers. The dramatic engine is the comparison the audience and the characters cannot stop making — what one brother has that the other doesn't.
The films above mostly refuse the easy resolution that the form invites. The Godfather's Michael does not save Fredo at the end; Fredo dies on his orders. The Tenenbaums do not, by the film's end, reconcile with their father in any morally clean way. The Fighter's Eklund is not, by the end, the brother Ward needed him to be. The films honour the genuine difficulty of fraternal relationships rather than resolving them for the audience's comfort.