In Croatia, Koseto families are Croats (from Pula ).
Prevalence
Only a few people with faimily name Koseto live in Croatia today, in one household only. There were 20 of them in the middle of the past century, and their number decreased significantly. They are located in one Croatian city only, in Pula (<5).
Outside Croatia
Family name Koseto (including: Cossetto , Cosetto ) is present in 10 countries worldwide. "Cosetto " is used by small number of people in the United States.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.