 Scholarly opinion had long considered Fiodor a Rurikid, rather than a Lithuanian, because of his Christian name.In 1916, however, a list of property belonging to Theognostus, a deceased Metropolitan of Moscow, and compiled in the 1330s, was published; among the items listed were two silver cups gifted by "Fiodor, brother of Gediminas".Margiris, the defender of Pilėnai, is often suggested as the most likely candidate for the fourth brother.