Ismailis share the following Imāms with the Twelver Shīʿah. However, there is dispute as to the numbering, as some[vague] branches refer to Ali as "first" while others refer to Hasan as the first. Further, some branches recognise Hasan as the successor to Ali, yet others Hussein and do not number Hasan. The Zaydi Shia branch broke from this chain after Ali ibn Husayn, following Zayd ibn Ali rather than Muhammad al-Baqir.
Ali (numbered as first by the Nizari, but not numbered by the Mustaali) born in 601 and died in 661.
Hasan ibn Ali (numbered by the Mustaali, not by the Nizari) born in 625 and died in 670.
Hussein ibn Ali (agreed to be the second Imam by both) born in 625 and died in 680.
The Ismaili split with the Twelvers over the succession to Imām Jaʿfar as they considered his eldest son Ismāʿīl as his heir. Whereas the Twelvers believe in the succession of Ismāʿīl's brother Imam Musa al-Kazim, the Seveners and the Ismāʿīlīs believe in the succession of Ismāʿīl and after him, his son Muhammad ibn Ismāʿīl.
Ismāʿīl (إسماعيل إبن جعفر), Jaʿfar's son and designated heir, predeceased his father in 762 but accepted as Imām by the Seveners and the Ismāʿīlīs (but opposed by the Twelvers). Born in 722 and died in 762.
Muhammad (محمد إبن إسماعيل), Ismāʿīl's son, died under the reign of Harun al-Rashid (786–809), born in 740 and died in 813.
The group that believed Muhammad ibn Ismail to be the Mahdi who had withdrawn into occultation and would return again to earth some day, came to be known as the Seveners. This term is often incorrectly applied to the "Ismailis" who had separated from the Seveners and gone further on with the succession to the Imamat.
One group of the Seveners propagated their faith from their bases in Syria through Dāʿiyyūn ("Callers to Islām"). In 899, the Abdallah al-Mahdi Billah|fourth Da'i announced that he himself was the "Imam of the Time" being also the fourth direct descendant of Muhammad ibn Ismail in the very same dynasty. This caused a split between his Sevener followers accepting his claim and those Seveners disputing his claim and clinging to Muhammad ibn Ismail as the Imam in occultation. This Imam and Fourth Da'i, Abdallah al-Mahdi Billah, eventually became the First Fatimid Caliph. This separated group from the Seveners now became known as the Fatimids of the Maghreb and Egypt. This was the reason why the Qarmatians, the original Seveners, were the Fatimid's most irreconcilable opponents.
In the Fatimid (and subsequently Ismaili) tradition, the Imamate was held by:
Al-Ḥākim bi-Amrillāh, 6th Fatimid Caliph, disappeared 1021. The Druze believe in the divinity of all Imams and split off after Hakim's disappearance, believed by them to be the occultation of the Mahdi.
After his death, the succession was disputed. The regent Malik al-Afdal placed Mustansir's younger son Al-Musta'li on the throne. This was contested by the elder son an-Nizar, who was defeated and died in prison. This dispute resulted in the split into two branches, lasting to this day, the Nizari and the Mustaʿlī.
Hafizi Ismaili Muslims claimed that Al-Amir died without an heir and was succeeded as Caliph and Imam by his cousin Al-Hafiz. The Mustaʿlī split into the Hafizi, who accepted him and his successors as an Imam, and the Tayyibi, who believed that Al-Amir's purported son At-Tayyib was the rightful Imam and had gone into occultation.
The Tayyibi branch continues to this day, headed by a Da'i al-Mutlaq as vice-regent in the imam's occultation. The Tayibbi have broken into several branches over disputes as to which Da'i is the true vice-regent. The largest branch are the Dawoodi Bohra, and there are also the Sulaimani Bohra and Alavi Bohra.
Daud Al-Hamid-lil-lah, son of Al-ʿĀḍid li-Dīn Allāh, 25th Hafizi Ismaili Imam, d. 1207/8 AD. Died in Prison under the Ayyubid dynasty.
Sulayman Badruddin, son of Daud Al-Hamid-lil-lah, 26th Hafizi Ismaili Imam, d. 1248 AD without issue. Died in Prison under the Ayyubid dynasty. The Hafizi Ismaili Imamah ended with him.
The Hafizi Ismaili sect lived on into the 14th century AD with adherents in Northern Egypt and Syria but had died out by the 15th century AD.
Offshoot of the Muhammad-Shahi Nizari Ismailis who follow the elder son of Shamsu-d-Dīn Muḥammad named ‘Alā’ ad-Dīn Mumin Shāh, follow this line of Imams until the disappearance of 40th Imam Amir Muhammad al-Baqir in 1796.