The 16th - century Ragusan historian Mavro Orbini , writing of Tuartco Scuro ( Tvrtko the Plain ) , claimed that he was born to Tvrtko I 's concubine , a Bosnian noblewoman named Vukosava .
This view was taken for granted by subsequent writers .
The 16th - century Ragusan historian Mavro Orbini , writing of Tuartco Scuro ( Tvrtko the Plain ) , claimed that he was born to Tvrtko I 's concubine , a Bosnian noblewoman named Vukosava , and this view was taken for granted by subsequent writers .