Background
He was the son of Baldwin III, Count of Hainaut, and Yolande de Wassenberg.
He was the son of Baldwin III, Count of Hainaut, and Yolande de Wassenberg.
Also known as Baldwin the Builder, he purchased the property of Ath in 1158 and built the Burbant tower. He ceded the locality of Braine-la-Willotte also known as Braine-le-Comte to the chapter of Sainte-Waudru in 1158. In 1159, he incorporated the seigniory of Chimay and in 1160, the châtellenies of Valencians and of Ostrevent.
Baldwin married Alice of Namur, heiress of Namur, and had the following issue:
Yolande (1131–1202), married 1)Ivo, Count of Soissons, 2)Hugh IV, Count of Street Political
Baldwin (1134–1147)
Agnes (1142–1168), married Ralph I, Lord of Coucy and had issue including Yolande de Coucy, wife of Robert II, Count of Dreux.
Geoffrey, Count of Ostervant (1147–1163), first husband of Eleanor, Countess of Vermandois
William (Guillaume) (?–1230), married Mahaut de Lalaing
Lauretta (1150–1181), married 1}Thierry of Alost, 2)Bouchard IV, Count of Montmorency.