In Croatia, Trojka families are Croats (from Cazma area ). In the past century, relatively most of Croatian residents bearing this family name were born in Bjelovar and in Cazma area.
Prevalence
About 10 people with faimily name Trojka live in Croatia today, in three households only. There were 10 of them in the middle of the past century, and their number remains constant. They are located in only one small Croatian place, in Starine in Cazma area (15).