Thank you so much for looking this up for me. A volunteer at the Clinton County Historical Society also saw my post and sent me some great material. Between your information and hers I can confirm that everyone you found is part of this family, and that my original information was wrong.
Deborah Roberts died early on and James, Sr. married (2) Mary ____ and (3) Sarah Thornton. Sarah died in 1880--which is why their young son Austin is living with his maternal grandfather Ira Thornton, I suppose.
James married to Enola is the son of James L Hamer, Sr. and his second wife Mary, I think. Her obituary gives her brothers' last name as Miller; do you think Elisher Niles could be Elisha Miller?Francis is also a son of James and Mary. I could find no children old enough to be those of the marriage to Deborah Roberts; perhaps there were none. Byron and his younger brother William K. married sisters named Oswalt from Alliance, Ohio and stayed in Clinton Co. James Sr's brother Joseph (d. 1892) and wife Mary R. Worden are in the 1870 census and buried at Oak Ridge cemetery in Bengal Twp.
James, Sr.'s absence from the 1880 census, or at least its index, is a mystery. He died in 1883 and is buried in Mountain Rest Cemetery, St. John's, Clinton Co. The most likely explanation I can come up with is that his name was misread or skipped by the person who made the census index.
I'm assembling all of this information into a report and sending it to the Clinton County Historical Society for their files. If anyone else wants a copy I'll be happy to send it.
I'm still looking for James, Sr.'s first cousin James Hamer, born in Union Co, PA before 1815. His brother wrote in 1842 that James left Watsontown, Northumberland Co, PA ca. 1837, got married in Michigan "two years back " and "died two weeks later." If you stumble across a trace of him I'd love to know about it. It was in looking for him that I found the Bengal Twp. Hamers, and recognized them as his cousins from New York. (There were Wards in that family as well, and I think some of them came to Michigan. Any relation?)
Thanks again. Your information has been very helpful and I appreciate your taking the time to do this.