Little is known about his life. He was born , the elder son of John Doukas by his second wife Zoe Doukaina. He may be identical to the Constantine Doukas who on 12 April 1204, on the eve of Constantinople's fall to the Fourth Crusade, competed with Constantine Laskaris for the imperial crown. Around 1208, he accompanied the deposed Byzantine emperor Alexios III Angelos, who had sought refuge in the Epirote court, to the Sultanate of Rum. From there, with Turkish support, Alexios unsuccessfully tried to take over the Empire of Nicaea.