Hi, Fayth, I attempted to email you, but it bounced back to me.
Unfortunately, I don't have much more information than you do about the Evjens. I believe Peder O. Evjen had a brother Johanes O., however. In the 1880 census, they are both living in the household of Sivert Berg. This isn't proof that they are brothers, but it seems likely. They share the same middle initial, O, suggesting their father's name began with the same letter.
I'm sorry I couldn't be of more help. I have no record of Peder after 1880, and no record of Peder and Maria's children after the 1900 census. Do you know where they went after that? Does your husband know where his grandparents/great-grandparents grew up?