In 1509 he married Margaret of Angoulême,[2] sister to Francis, Duke of Valois, who would in 1515 become King Francis I of France. Their marriage was childless: his wife was allowed to retain most of his titles.
As first prince of the blood, Charles was a prominent figure in the early part of his brother-in-law's reign. Made governor of Normandy,[3] Charles fought at Marignano in 1515,[4] and in 1521 defended Champagne against an imperial invasion. He accompanied his brother-in-law, King Francis I of France, on his second expedition to Italy in 1525, and after the disaster at Pavia, took command of the defeated French forces, leading them in retreat back to French territory.[5] He was made a scapegoat for the defeat and accused of abandoning the king, and died soon after.[5] Although Charles had a sister, Françoise, who survived him, his widow took possession of his lands after his death.