As I watched the movie last night it was obvious to me that if one took the Sullivan brothers out of history and into an RPG world, they would be the cause of many adventures. Here are a few ideas that I came up with:
Adventure hooks/plots based on The Fighting Sullivans
Honestly, just about any scenario can be livened up by a group of five capable, loyal and organized brothers as allies or antagonists.
The PC's owe the five brothers a debt of honor, which entails providing for their dependents after they're dead. This includes one very attractive widow.
The five have been hired for a mission directly in opposition to the PC's mission.
The five have been hired for a mission in competition with the PC's mission.
The five brothers have a Destiny upon them and all five must survive long enough to fulfill it, to prevent Big Badness. The PC's are responsible for their survival during the big mission leading up to the Fulfilling of the Destiny.
One of the five is lost/missing/kidnapped/captured and the remaining four hire the PC's to help recover the fifth.
A Patron hires the PC's to eliminate the five brothers, as they stand between the patron and a large inheritance.
The five brothers are a super-hero or secret agent team, and the PC's have discovered their identities.
Gender flip: it is a family of five fighting women. Gender split: a family of 3 men 2 women or 3 women 2 men that all operate together.
My wife is a big fan of audio books. We love Librivox! Also we love borrowing books on CD from the public library to listen to in the kitchen or in the car on long trips. My wife is a big fan of Agatha Christie and Elizabeth Peters, so:
Adventure based on Agatha Christie's Cat Among the Pigeons:
The PC's have been hired to be covert security for a student at a private academy, and must take civilian jobs on the academy campus. No heavy weaponry is going to be allowed. This should be a brains not brawn assignment.
Adventure based on the Amelia Peabody series:
The PC's get involved in an archaeological expedition, either as security, as the dig leaders, or even as porters/staff. During the dig, rare and valuable macguffins are uncovered, stolen and in need of recovery. There may be international forces involved in the thefts. Murder of the archaeologists is not out of the question. A war may start up during the dig, which may or may not have anything to do with the dig itself. Depending on the genre, the macguffins could be magical or mystical.