In Croatia, Modrošić families are Croats (from Sisak ). In the past century, relatively most of Croatian residents bearing this family name were born in Sisak.
Prevalence
Only a few people with faimily name Modrošić live in Croatia today, in four households only. There were 20 of them in the middle of the past century, and their number halved. They are located in only one small Croatian place, in Lonja (<10).
Outside Croatia
Family name Modrošić is present in two countries on two continents. The family name "Modrosic " is used by small number of people in the United States.