Mehmed's claim rested principally with the idea that Constantinople was the rightful seat of the Roman Empire, as it had indeed been for more than a millennium even if the 1204-1261 period is subtracted. Contemporary scholar George of Trebizond wrote that "the seat of the Roman Empire is Constantinople (...) and he who is and remains Emperor of the Romans is also the Emperor of the whole world". An additional though questionable claim of legitimacy referred to the past alliances between the Ottoman dynasty and Byzantine Imperial families. Byzantine Princess Theodora Kantakouzene had been one of the wives of Orhan I, and an unsupported but widespread story portrayed Mehmed as a descendant of John Tzelepes Komnenos.