Nawab Qasim Jan was a courtier in the royal courts of Mughal Delhi.[1] According to some sources he came from Yarkand and first lived in Lahore, attached to the court of the Governor Moin-ul-Mulk in the 1750s, thereafter he moved to Delhi and joined the Mughal court under emperor, Shah Alam II (r. 1728–1806).
Soon he was given the title of Nawab and Khan, and given the region of Hateen near Gurgaon and thereafter he built his home close to Red Fort, in Ballimaran, Delhi, in the lane that is still known as Gali Qasim Jan, and also built mosque nearby known as Qasim Khani Mosque.[1] He had two brothers, Alam Jan and Arif Jan,[2] whose son, Ahmad Baksh Khan, later founded the princely state of Loharu (now in Bhiwani district) in 1806.[3] Noted Urdu poet, Mirza Ghalib was married to Umrao Begum, daughter of Nawab Ilahi Bakhsh Khan (younger brother of the first Nawab of Loharu, Ahmad Baksh Khan); Ghalib ki Haveli, the poet's residence in Delhi, was in Gali Qasim Jan and is now a museum.
His son, Nawab Faizullah Beg, was a courtier during emperor Bahadur Shah Zafar's reign, and built a complex later known as Ahata Kaley Sahab, so named after saint Kaley Khan, who lived here for a while, after whom Delhi's Sarai Kale Khan is also named. The complex was later acquired by Bunyadi Begum, poet Mirza Ghalib's sister-in-law, and housed the poet after he was released from debtors' prison.[1][4]