Ishaq was a member of a collateral branch of the Abbasid royal dynasty, being a first cousin of the first two Abbasid caliphs al-Saffah (r. 750–754) and al-Mansur (r. 754–775).[3] His father, Sulayman ibn Ali, had been a senior member of the family during his lifetime and had held the important governorship of Basra during the initial years following the Abbasid Revolution.[4] He was also connected to the ruling line by his marriage to Aliyah, the daughter of al-Mansur and an Umayyad woman.[5]