Welcome, Vadim Verenich
Try to contact Croatian genealogical society "Hrvatsko rodoslovno društvo-Pavao Ritter Vitezović"- http://www.rodoslovlje.hr/
(you can find email on - O društvu --> Kontakt.)
Croatian surnames are analyzed in books of Petar Šimunović, newest is Hrvatski prezimenik (on this forum we have topic about surnames- Prezimena - http://www.forum.hr/showthread.php?t=93460&page=45
, it is possible to get some short info from Šimunović's books)
For informations about people and surnames from 14.century only reliable sources are documents stored in historical archives (Državni arhiv Split
and better for this,Državni arhiv Zadar
). But if something is not publicated, then....come to archive and try to "dig out" alone (money,time,enormous patience) or contact and employ proffesional researchers (expensive).
You can find surname Vrančić in small town Vrlika.
Also, i need to mention bishop Antun Vrančić, from Šibenik, died 1573. in Presov (Slovakia). In hungarian registers he was named- Antal Verancsics.
There is also similar toponym Verunić (Verunich), village on Dugi otok island in Zadar archipelago.
first what attracted my attention, names of your ancestors Paszko, Simun, Hieronim and Dmitar are very very similiar to croatian names Paško, Šimun, Jeronim, Dmitar (Mitar). Especially, Paško and Šimun -these are "original" Croatian variants of names Pavel and Simeon, they are specific for Croatians living in region Dalmatia and you cant find them among orthodox Serbs or in Serbia.
So it makes little confusion for me when you mentioned in family legend that they were Serbians or came from Serbia.
Also period of mid-XV century when your ancestors settled land near Pinsk is parallel with period of military campaign of hungarian-croatian king Louis Anjou (Ludwik Węgierski ) in medieval Polish-Lithuanian union.
In 1370. he was crowned as king of Poland, so he established political relations between Croatian and Hungarian kingdom and Polish-Lithuanian commonwealth. So it became almost as one state under strong rule of Ludwik.
In my opinion,it is possible that some people from Croatia in millitary service arrived in Poland, as vassals/soldiers/mercenaries of their king Ludovik/Ludwik, and settled area where they received king's land as benefit and mark of their favour and loyality
sorry, need to refresh my English