His father came from the Aromanian village of Dolna Belica,[1][2] where his cousin Cincar Marko Kostić, another leader in the Serbian Uprising was born.
After he had murdered a certain Turk, Janko fled northwards and around the year 1800 and settled in Valjevo where he lived as a tradesman.
[3] When the outlawed janissaries from Belgrade decided to preemptively murder all the important Serbs in the district they controlled, Popović was also imprisoned, but was in the end released due to the pleading of many citizens of Valjevo.
Cincar Janko distinguished himself in the battle of Mišar (1806) and in the consequent pursuing of the defeated Bosnian army during which he even crossed into the Habsburg Empire to attack those who sought refuge there.
During the 1813 Ottoman offensive Cincar Janko was defending Deligrad on the southern front but had to retreat, first to Požarevac and then to Belgrade, where from he crossed to the Habsburg Empire.
Because of the 1809 border incident Cincar Janko was now put to trial and imprisoned in Arad.
His sons got educated as officers of the Russian army in which they started their career but later returned to Serbia with their father.