He was the son of Henry II of Brabant and Marie of Hohenstaufen.

The disputed territory of Lothier, the former Duchy of Lower Lorraine, was assigned to him by the King Alfonso X of Castile, a claimant to the German throne.

Alfonso also appointed him imperial vicar to advance his claims on the Holy Roman Empire.

In 1251, he married Adelaide of Burgundy (c. 1233 – October 23, 1273),[1] daughter of Hugh IV, Duke of Burgundy and Yolande de Dreux, by whom he had four children: On February 26, 1261, Henry III signed his will, which included a clause threatening to banish Jewish people from Brabant unless they ceased the practice of usury, albeit only after his death.

His wife Adelaide, acting as regent since Henry IV was incapable of ruling, never enforced this policy laid out in the will, and the Jews were able to stay.