Imamate in Twelver doctrine
…Each Imam was the son of the previous Imam, with the exception of Husayn ibn Ali, who was the brother of Hasan ibn Ali. The twelfth and final Imam is Muhammad al-Mahdi, who is believed by the Twelvers to be alive and in hiding. The office of imamate is bestowed upon the figure of imam (lit. 'leader' or 'master'), whose…