The link I provided states Vrpolje, as his birthplace. Possible confusion is the location of Vrpolje in Croatia. I see now that there is at list one more Vrpolje and in the area closer to the Adriatic coast. However, Mestrovic's Vrpolje is North of river Sava.
I see on some of the old maps that some of the tribal nations reached the river Sava but likely did not go much further South. If that Vrpolje is the correct birthplace, this will be very close to the A-H Military Frontier zone (1553–1881) which expanded in a large loop. Many ethnic groups from South and North moved to these zones for economic and other reasons. From 1700 until mid-1800 this area and going East to Serbia (North of Dunav and Sava) had influxes of Slovaks, Germans, Serbians and others. Also, swapping some of the Slavik villages with Hungarian population (Magyarization) and movements of Croatians and Serbians in all of the directions, as discussed in other forums. Looking at Y-DNA of Hungarians and even the history of some of their last names, it should support this way of thinking.
Is this area really with a population of very similar Y-DNA %? Maybe it was not at Ivan Mestrovic birth time? Bachka, Banat, and Slavonia being above very large rivers like Sava and Danube (barrier in the past and natural border), and the Military Frontier migration targets, I would expect some differences.
