Louis VIII of France
Blanche was the eldest daughter of John I, Marquis of Namur and Marie of Artois. On her father's side, she was a member of the powerful House of Dampierre, being a grandchild of Count Guy of Flanders. On her mother's side Blanche was related to the French royal house, as her mother was a daughter of Philip of Artois, a patrilineal great-grandson of Louis VIII of France, and thus a member of a junior line of the House of Capet.