Margaret of Hungary Empress consort of Isaac II Angelos, Byzantine Emperor (b. 1175) Parents Agnes of Antioch Béla III of Hungary Children John Angelus of Syrmia William V of Saint Omer Bela of Saint Omer Demetrius of Montferrat Siblings Emeric, King of Hungary Constance of Hungary Andrew II of Hungary Partners Nicholas I of Saint Omer Isaac II Angelos Boniface I, Marquess of Montferrat