Sanjak of Kyustendil
A very interesting fact is that there is a preserved document according to which in Kyustendil in 1570 there was a professional chess player. 
The Kyustendil Pasha was the first to be mirmiran in the Ottoman Empire because of the glorious military history of the city with the Battle of Velbazhd and because of Konstantin Dragash, who is the grandfather of the last Roman emperor (Constantine XI Dragases Palaiologos) and at the same time the great-great-grandfather of the first Russian tsar (Ivan the Terrible). 
- THE KYUSTENDIL SANJAK IN THE XV-XVI CENTURY, p. 148
- Енциклопедичен речник Кюстендил, стр. 337. БАН. 1988.