According to the information at http://familysearch.orghttp://familysearch.org the Nathan Nivison you are researching was married twice. He had 8 children by Ann and then 2 more by his second wife.
The Nathan on the 1870 Branch County Michigan Census is a brother to Samuel - the father of the Nathan you are researching. The other Nivisons in the Algansee Twp are children of Nathan and Mathilda. Sorry they aren't the family you are searching for.
Hope you can find the information you are searching for.