He was a Member of the 3rd National Assembly of Pakistan, representing the Sylhet-V (Habiganj) constituency.
His great grandfather, Syed Mir Qadir Bakhsh, belonged to the Syed family of Malidia in Faridpur but Bakhsh's son, Syed Mir Sarwar Jan (d. 1914), migrated to Bamna in greater Barisal after marrying Azizunnesa, the daughter of Taluqdar Husayn ad-Din Chowdhury, and eventually inheriting the taluqdari of Ramna-Bamna.
The second brother, Syed Ziaul Ahsan, was a speaker for the East Bengal Legislative Assembly during the United Front regime and married to Syeda Shaukat Ara Begum, the daughter of Syed Abdul Jabbar, a zamindar of Comilla.
Syeda Sajeda Chowdhury, the incumbent deputy leader of the Jatiya Sangsad, is the daughter of Qamarul Ahsan's cousin Syed Shah Hamidullah.
[1] Qamarul Ahsan was a Member of the 3rd National Assembly of Pakistan representing Sylhet-V (Habiganj Subdivision).