Jacob's Biblical twin is Esau, who appears in the Old Testament of the Bible. He was the son of Isaac and Rebekah, and the brother of Jacob. Esau was the firstborn son of Isaac and Rebekah, and was favored by his father. Jacob, however, tricked Esau out of his birthright and received the blessing of his father instead. This caused a rift between the two brothers, and they eventually reconciled.