Semialjac families are Croats and they are mostly from Nasice area. In the past century, relatively most of Croatian residents bearing this family name were born in Nasice area and in Nasice.
Prevalence
About 130 people with faimily name Semialjac live in Croatia today, in 60 households. There were 140 of them in the middle of the past century, and their number decreased by 10 percent. They are located in 10 Croatian counties, in 11 cities and 11 other places, mostly in Koska in Nasice area (95), Zagreb (15), Osijek (<10), Rijeka (<10), and in Petrijevci in Valpovo area (<10).
Outside Croatia
Family name Semialjac is present in four countries on two continents.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 2007 in source Encyclopaedia of Croatian Surnames.