Asael was the fifth son of David and Beila Bielski, who had a total of twelve children: ten boys and two girls. He was two years younger than his brother Tuvia, who later commanded the Bielski Otriad. The Bielskis were the only Jewish family of Stankiewicze, a small village in pre-war Poland, currently Western Belarus. It was located between Lida and Navahrudak (called Nowogródek in Polish), both of which later housed Jewish ghettos during World War II. He was quieter and more reserved than his brothers, and was content to stay on the farm and around those he knew well.
