The "Father" of Christianity, Islam, and Judaism is Abraham. Abraham called the "Father" of Christianity, Islam, and Judaism because those three faiths are originated from Abraham descendant. In the Bible of Christianity, Matthew list every ancestor of Jesus from his father Joseph that leads to Isaac, the son of Abraham. Abraham had another child named Ishmael, who later made the Ka'aba, Islam's holiest shrine. As for Judaism, Abraham is the first person who has faith in one God, which is the Yahwe from the holy Jewish text.
