The surviving records on the internal history and rulers of the Emirate of Crete are very fragmentary.
He is tentatively identified as a son of the third emir, Abu Abdallah Umar (II), and the grandson of the conqueror of Crete and founder of the emirate, Abu Hafs Umar.
[1][2][3] In 909/10, the unnamed author of the hagiography of Theoktiste of Lesbos was sent to Crete as an envoy to ascertain whether the local Arabs would make common cause with the Abbasid fleets operating from Syria.
[4] In 911, the Byzantines launched a large-scale expedition, with over 100 ships and 43,000 men, to recapture the island, but were driven off.
[4][5] Yusuf is presumably the unnamed Emir of Crete addressed in a letter by Patriarch Nicholas I Mystikos in 913/14.