Boleslaw, the son of Mieszko I and of his first wife, the Bohemian princess Dubrawka, had in 984 married an unknown daughter of Rikdag, Margrave of Meissen, and subsequently married Judith Arpad, a daughter of Geza, Grand Duke of Hungary; then Emnilda, daughter of Dobromir; and lastly Oda, another daughter of the Margrave of Meissen.

His wives have borne him sons, including Bezprym, Mieszko II and Otton; and a daughter, Mathilde.

After his father's death around 992, Boleslaw had expelled his father's second wife, Oda von Haldensleben, and her sons, thereby attempting to unite Poland again.

Boleslaw has inherited from his father his principality, centered on Greater Poland, being along the river Warta ("valley of Warta"), and much smaller than modern Poland.

By 1997, Boleslaw already possesses Silesia and the eastern parts of Pomerania (with its chief city, Gdańsk) and Lesser Poland (with its chief city, Kraków).

Boleslaw sends Adalbert of Prague to Prussia, on the Baltic Sea, in 997 on a mission to convert the heathen Prussians to Christianity—an attempt that will end in Adalbert's martyrdom and subsequent canonization.