In Croatia, Sustolčić families are Serbs. In the past century, relatively most of Croatian residents bearing this family name were born in Hrvatska Kostajnica.
Prevalence
Only a few people with faimily name Sustolčić live in Croatia today, in one household only. There were 10 of them in the middle of the past century, and their number decreased significantly. They are located in one Croatian city only, in Sisak (<5).
Outside Croatia
Family name Sustolčić is present in this form only in Croatia.