He was the son of Caesar John Ducas, brother of the emperor Constantine, (Ducange, Fam. Byzant. p. 165.) Nicephorus Bryennius applauds his virtues and extenuates his faults, (l. i. p. 30, 38. l. ii. p. 53.) Yet he owns his enmity to Romanus
Scylitzes speaks more explicitly of his treason.