In Croatia, Kocaj families are mainly Croats (from Middle Bosnia ), less frequently Ukrainians (from Middle Bosnia ). In the past century, relatively most of Croatian residents bearing this family name were born in Middle Bosnia (Sarajevo area) and in Middle Bosnia (Skender Vakuf area).
Prevalence
Only a few people with faimily name Kocaj live in Croatia today, in two households only. They are located in only two Croatian places: in Ivanja Reka (<5) and Sesvete (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned over five times, the first time 1925 in source Emigration Commission Zagreb.