They maintained that Ali, a relation and the adopted son of Mahomet and husband of his daughter Fatima, was the first legitimate imam or successor of the prophet.

The sixth imam, Jaffer, upon the death of his eldest son, Ismail, appointed another son, Moussa or Moses, his heir; but a large body of the Shiahs denied the right of Jaffer to make a new nomination, declaring the imamate to be strictly hereditary.