Bolesław was the eldest son of the Polish high duke Henry II the Pious by his wife Anna,[1] a daughter of the Přemyslid king Ottokar I of Bohemia.

Among his younger siblings were Mieszko (died 1242), Henry III the White (d. 1266), Konrad II (d. 1274), Władysław (d. 1270), and Elisabeth (d. 1265), who married her Piast cousin Duke Przemysł I of Greater Poland.

Bolesław succeeded as Duke of Silesia after his father, Henry II the Pious, was killed in the Battle of Legnica on 9 April 1241, fighting against the Mongol invaders led by Batu Khan.

The local nobles, led by the Kraków governor Clement of Ruszczy, strongly resisted but eventually had to yield to Konrad's superior forces.

To regain freedom, Bolesław signed an agreement with Henry III, dividing the Lower Silesian lands of Legnica and Wrocław.

To avoid further fragmentation, the two pledged to offer hospitality to their minor brothers, Bolesław to Konrad I, and Henry to Władysław.

Bolesław, as the eldest, got first choice of the districts, and he chose the Legnica estates, possibly because of the gold discovery in the Kaczawa and Wierzbiak Rivers.

Bolesław sought allies among the Ascanian relatives of his wife Hedwig, daughter of Count Henry I of Anhalt.

Archbishop Wilbrand of Magdeburg contributed funds after Bolesław sold half of Lubusz Land to him.

The final clash occurred two years later, when the Bolesław was defeated by the combined forces of Przemysł I and Henry III the White, who supported Konrad.

Bolesław made some agreements with the other Piast dukes, especially with the princes of Greater Poland and with Bishop Thomas I of Wrocław.

In 1273 he granted the Duchy of Jawor to his oldest son Henry V and it seemed that Bolesław had resigned from adventurous politics.

They had seven children: In 1261, Bolesław married secondly Euphemia (also called Alenta or Iolanta or Adelheid) (born c. 1245 - died c. 15 February 1309), daughter of Sambor II, Duke of Pomerania.