Cain- the first son of the first humans Adam and Eve killed his younger brother Abel because of jealousy with the attention God is giving to his brother's offerings
Napoleone & Allesandro- were brothers but rivals with two diff. political factions, they murdered each other not because of politics but because of their inheritance
Camicion de' Pazzi- murdered his relative Ubertino
Mordred- betrayed his uncle King Arthur and because of the battle that took place between the two nearly everyone died; although King Arthur killed him Mordred mortally wounded King Arthur as well