A member of the Abbasid dynasty, Abdallah was the descendant of notable personages on both sides of his family. His father Muhammad was a son of Ibrahim ibn Muhammad ibn Ali, who had been a leading figure in the early stages of the Abbasid Revolution before being killed by the last Umayyad caliph Marwan II in 749.[2] His mother, Zaynab, was the daughter of Sulayman ibn Ali and a senior princess at the Abbasid court, and Abdallah himself was usually known by the names of "al-Zaynabi" or "Abdallah ibn Zaynab."[3] He was a second cousin of the fourth and fifth Abbasid caliphs al-Hadi (r. 785–786) and Harun al-Rashid (r. 786–809).[4].