In Croatia, Sisek families are Croats (from Koprivnica area ). In the past century, relatively most of Croatian residents bearing this family name were born in Zagreb and in Koprivnica area.
Prevalence
About 30 people with faimily name Sisek live in Croatia today, in 11 households. There were 50 of them in the middle of the past century, and their number decreased by 50 percent. They are located in four Croatian counties, threee cities and 5 other places, mostly in Zagreb (10), Gorica in Koprivnica area (<10), Nedelisce in Cakovec area (<5), Komatnica in Koprivnica area (<5), and in Gorican in Cakovec area (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1938 in source Emigration Commission Zagreb.