In “The Singing Bone,” the younger brother kills a wild boar to win the princess.
The boar has been devastating the kingdom, and the king promises his daughter in marriage to whoever can kill it. The younger brother succeeds after a dwarf gives him a spear. His older brother, who has been drinking with companions to build courage, learns what happened and murders him on the journey back to the king.
The older brother then claims the victory and marries the princess. The crime is eventually exposed when a shepherd finds one of the younger brother’s bones beneath a bridge and makes it into a mouthpiece for a horn. The horn sings about the murder, leading the king to investigate and punish the guilty brother.
The tale is KHM 28 and belongs to Aarne–Thompson type 780. A common mix-up is remembering the story as a dragon-slaying adventure; some later adaptations replace the boar with a dragon, but the Grimm tale uses a wild boar.