Henry was deposed in 1267. Henry's brother, John I, Duke of Brabant married Margaret on September 5, 1270. John was said to be a perfect model of a feudal prince in the days of chivalry: brave, adventurous, excelling in every form of active exercise, fond of display, generous in temper. This made him very popular in Middle Ages poetry and literature. He was also famous for his many illegitimate children.
Margaret became pregnant in 1270/1271. Margaret gave birth to a son in 1271. Mother and baby did not survive and both died shortly after the birth.