I believe John Unbehaun was a brother to my 2nd great grandfather Guenther. I found both John and Guenther along with their families in 1860 in Auburn, Fond du Lac, Wisconsin. Guenther and his family came back to Michigan and I believe Harriet did as well. Maybe John died in Wisconsin?
Do you have any pictures of your Unbehauns? I saw a picture of Mary posted and it looks very close to a picture I have in one of my photo albums, maybe we could make a match!