The Musta‘lī Ismā'īlī Muslims are so named because they accept al-Musta‘lī as the nineteethFatimid Caliph and legitimate successor to his father, al-Mustansir. (In contrast, the Nizāriyya — presently headed by the Aga Khan — believe the rightful nineteeth caliph was Musta‘lī's brother, Nizār.) The Musta‘liyyah are also referred to as the Taiyabi or Ṭayyibī after the last Imām they recognized, Ṭayyi… (More on Mustaali)