Sam is Max's brother. The two were constantly getting into trouble because of their use of the Normanomicon, having raised an army of Hollow Men in the Bowerstone Cemetery and unleashing a Banshee on the town of Bloodstone.
During the Rescuing Charlie sidequest, it is revealed that Sam and Max have also raided the Hero's Tomb at Bower Lake, and had managed to arm a trap that caused even more hollow men to appear.
After the Evil in Wraithmarsh sidequest, it was pointed out that Sam and Max's father was killed. All of the quests that have some sort of relation to Max & Sam involve hollow Men in some way, usually summoned by them.
He and his brother's name could be a reference to the episodic adventure game series, Sam and Max. It is also a reference to two brothers who work for Lionhead Studios. "Sam Spade" is also a stereotypical name for the pulp-fiction private investigator.
Trivia
- Sam, and his brother Max, seem to make an appearance in Fable III, seen in a video from Gamescom. It looks like they will be back as ghosts (guessing from their greenish, translucent appearance) and will be giving a quest titled Bored to Death.
- Sam and Max are more important than anyone could imagine, as they are a part of the prophecy in "The end is nigh". The prophecy in the book says that two brothers (Max and Sam) will unleash howling death (the banshee) to a town of blood (Bloodstone).