In Croatia, Kustec families are generally Croats (from Podrinje (Bosnia) ), barely Bosniaks (from Pula ), and . In the past century, relatively most of Croatian residents bearing this family name were born in Zagreb and Kutina.
Prevalence
About 50 people with faimily name Kustec live in Croatia today, in 20 households. There were 20 of them in the middle of the past century, and their number more than doubled. They are located in 7 Croatian counties, in 7 cities and four other places, mostly in Zagreb (25), Kutina (<10), Pula (<5), Repusnica (<5), and in Slakovec in Cakovec area (<5).
Outside Croatia
Family name Kustec is present in 7 countries on four continents. The family name "Kustec " is used by some 80 people in Canada , small number in the United States , and small number of people in Australia.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1925 in source Emigration Commission Zagreb.