In Croatia, Kosek families are almost entirely Croats (from Zagreb ), very rarely Bosniaks (also from Zagreb ). In the past century, relatively most of Croatian residents bearing this family name were born in Zagreb.
Prevalence
About 30 people with faimily name Kosek live in Croatia today, in 15 households. There were 40 of them in the middle of the past century, and their number decreased by 20 percent. They are located in two Croatian cities only, in Zagreb (40) and Zapresic (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned over ten times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.