According to "The Late Medieval Balkans, A Critical Survey from the Late Twelfth Century to the Ottoman Conquest" (1994) by J. V. A. Fine, Grgur was appointed governor of territories of southern Serbia associated to the House of Branković.
Potrivit lucrării „The Late Medieval Balkans, A Critical Survey from the Late Twelfth Century to the Ottoman Conquest” (1994) de J. V. A. Fine, Grgur a fost numit guvernator al teritoriilor din sudul Serbiei asociate Casei Branković.