He was a younger son of
Bela of Saint Omer and
Bonne de la Roche, sister of the
Lord of Athens and Thebes,
Guy I de la Roche. Upon their marriage, in 1240, Guy gave Bela the lordship over half of
Thebes. John participated, along with his brothers
Nicholas II and
Otho, in the
War of the Euboeote Succession in the ranks of the coalition of most of the princes of
Frankish Greece, who opposed the expansionist policies of the
Prince of Achaea,
William II of Villehardouin. John married
Margaret of Passavant in 1276, but was unsuccessful in securing her inheritance of the
Barony of Akova in the
Principality of Achaea, which had been appropriated by the Prince after the death of baron
Walter of Rosières. Despite the support of his brother Nicholas, he managed to receive only a third of the barony (eight fiefs), as well as the post of hereditary
marshal of the Principality. From his marriage he had one son,
Nicholas III of Saint Omer. ==References==