Torvald Kolseth/Kjolseth

Looking for help in locating where Torvald Kolseth and Emil Bernh Kolseth are from. I can't seem to find them prior to 1875. Torvald Kjolseth b. 1831 married Marie Secilie Arnesen. They were living in Fredrikstad in 1875 census. His brother? Emil Bernh Kolseth b. 1859 married Anna Arnesen. Kolseth seems to be an unusual name and I don't see it listed in other census records. Any help would be great thanks!