As evidenced by his nisba, Ammar hailed from the Arab Banu Kalb tribe, and belonged to an aristocratic family established in Ifriqiya since the Muslim conquest of the Maghreb. The family had evidently embraced the Fatimid regime after the overthrow of the Aghlabids in 909, and his father Ali had served the Fatimids with distinction, being killed by the rebellious populace in Agrigento in 938. Along with his brother Hasan, Ammar belonged to the close circle around Jawdhar, the powerful chamberlain and chief minister of Caliph al-Mansur bi-Nasr Allah.[1][2]