Fazlul Karim was born on 30 Choitro 1289 BS (1882) to the Bengali Muslim of Sardars in the village of Kakina Bazar which was then located in Lalmonirhat, Rangpur district, Bengal Presidency.

He was the second of the five sons and three daughters of Amirullah Sardar and Kokila Bibi.

At the age of eleven, he published his first handwritten book of poetry, Shorol Poddo Bikash.

[1] Fazlul Karim married Basirunnesa Khatun when he was 13 years old.

[1] Karim wrote his first book at the age of eleven, entitled Sarol Paddo Bikash.