Isma'il Ibn Jafar
Isma‘il ibn Ja‘far (Arabic: إسماعيل بن جعفر; c. 721 CE/103 AH – 755 CE/138 AH) was the eldest son of Imam Ja'far al-Sadiq and the full-brother of Abdullah al-Aftah. Following Ja'far's death, the Shia community split between the element that would become the Twelver Shia, and those who believed the Imamate passed through to Ismail's son; the Ismaili branch of Shia Islam is accordingly named for Ismail. According to both the Nizari and Mustaali Shia sects, he is the sixth Imam. He was buried in Jannat al-Baqi.
Read more about Isma'il Ibn Jafar: The Ismaili-Ithna’asheri Division, Imam Ismail and The Commencement of The Dawr-al-Satar (Ismaili Period of Concealment), The Fatimid Caliphate, The Nizar-Mustali Division, Succession, Biography