Grgur was the second son of sevastokrator Branko Mladenović,[1] the governor of Ohrid under Emperor Dušan (fl.
Grgur was first mentioned in March 1347, as a kesar, in a letter from Pope Innocentius VI to Emperor Dušan.
[3][4] Grgur is mentioned in charters authored by Dušan dating to 1348–54 of the Monastery of the Holy Archangels in Prizren, which point to that Grgur held a region around Prizren.
[5] Grgur and bishop Grigorije of Devol founded the Zaum monastery (Church of the Holy Virgin Zaumska, Bogorodica Zahumska) on Lake Ohrid near Zaum, to which he brought the cult of the Virgin of Zahumlje (hence its name).
[6] A Grgur ruled the oblast (province) of Polog, in what is today northwestern North Macedonia, but it is uncertain whether this is the same Grgur or some otherwise unknown noble.