His father ruled Kumanovo with a district spanning from Preševo to Velbazhd (Kyustendil). After his father"s death, the young brothers Jovan and Constantine were taken care of by Vlatko Paskačić, at the order of the Mrnjavčevićs, who continued to rule the region until Jovan reached adolescence.
He later became an Ottoman vassal after the Battle of Maritsa in 1371. Ottoman sources report that in 1373, the Ottoman army compelled Jovan (who they called Saruyar) in the upper Struma, to recognize Ottoman vassalage. After the Battle of Maritsa, the two brothers became Ottoman vassals as the Mrnjavčevićs were defeated.
They, however, continued to rule their region as a semi-independent state, and managed to further expand their father"s district, taking territory from Jovan Oliver.
He issued coins that were of same design as those of Vukašin Mrnjavčević. He donated the Saint Basil"s church in Štip to the Hilandar monastery.
