The term 'Brother of Cain' refers to two biblical figures, ABEL and Seth. ABEL was the first son of Adam and Eve, and the brother of Cain, who killed him out of jealousy. Seth was the third son of Adam and Eve, born after ABEL's death. He is also considered to be the brother of Cain. Both ABEL and Seth are important figures in the Bible, and their stories are often used to illustrate the consequences of sin and the power of faith.