As the Papacy supported the claims of Walter VI of Brienne on the Duchy of Athens, James (along with his father and his brother Peter) was among the Catalan leaders excommunicated on 29 December 1335 by William Frangipani, Latin Archbishop of Patras.
[1][2] In accordance with their father's will, James succeeded in the domains of his older brother Peter—the County of Salona, the baronies of Loidoriki, Veteranitsa, and perhaps Zetouni—after the latter died childless sometime before 1355.
These possessions had been confiscated by the Crown of Aragon a few years before, but James was apparently successful in securing their return through the mediation of an embassy sent by the Catalan lords of Greece to King Frederick III.
[3][4] The same embassy petitioned to remove the incumbent vicar-general, Raymond Berardi, and to install James in his stead, but it is unclear whether this request was granted.
[7] In 1365, James seized the fortress of Siderokastron from the marshal Ermengol de Novelles, who had been declared rebel for refusing to surrender it to the appointed vicar-general, Matthew of Moncada.