[1] Khan was born in the 16th century into an aristocratic Bengali Sunni Muslim zamindar family known as the Dewans of Sarail in the Sultanate of Bengal.
His father, Dewan Sulaiman Khan (formerly Kalidas Gazdani), inherited this position and converted to Sunni Islam.
Ismail Khan's mother, Syeda Momena Khatun, was the daughter of Sultan Mahmud Shah.
During the reign of Islam Shah Suri in 1545, Muhammad Khan Sur was appointed as the Governor of Bengal and responsible for warding off rebellious chieftains in the region.
Ismail, and his elder brother Isa Khan, were subsequently taken as captives and later sold as slaves to Iranian traders in Turan.