In Croatia, Sumonja families are generally Croats (from Hrvatska Kostajnica area ), very rarely Serbs. In the past century, relatively most of Croatian residents bearing this family name were born in Hrvatska Kostajnica area and in Zagreb.
Prevalence
About 20 people with faimily name Sumonja live in Croatia today, in 6 households. There were 0 of them in the middle of the past century, and their number multiplied. They are located in threee Croatian counties, four cities and threee other places, mostly in Rujevac in Hrvatska Kostajnica area (<10), Velika Mlaka (<5), Rijeka (<5), Voloder in Kutina area (<5), and in Sisak (<5).
Outside Croatia
Family name Sumonja is present in 9 countries on four continents. The family name "Sumonja " is used by some 70 people in France , small number in the United States , and small number of people in Germany. "Sumonia " 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 over ten times, the first time 1917 in source List of Dignitaries, Officials and Public Servants of the Kingdom of Croatia-Slavonia.