The Ismā'īlī doctrine of Imāmah differ from that of the Twelvers because they had living imams for centuries after the last Twelver Imam went into concealment. They followed Isma'il ibn Jafar, elder brother of Musa al-Kadhim, as the rightful Imam after his father Ja'far al-Sadiq. The Ismailis believe that whether Imam Ismail did or did not die before Imam Ja'far, he had passed on the mantle of the imāmate to his son Muḥammad ibn Ismā'īl al-Maktum as the next imam.