Mieszko I of Poland
Boleslaus was an elder son of Duke Boleslaus I the Cruel and brother of the three other children of his father who survived to adulthood: Strachkvas, Doubravka (the wife of Duke Mieszko I of Poland) and the abbess Mlada. His mother may have been Biagota, a mysterious figure known only from her coins. According to some historians, she was the wife of Boleslaus I.