In Croatia, Kastelac families are Croats (from Sisak ). In the past century, relatively most of Croatian residents bearing this family name were born in Sisak.
Prevalence
Only a few people with faimily name Kastelac live in Croatia today, in two households only. There were 10 of them in the middle of the past century, and their number decreased significantly. They are located in only two naselja i to in Sisak (<5) and Staro Pracno (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.