Tristan- I think I have a good possibility for you. First, if your Great Grandmother was 83 when she died in 2008, she was born about 1925 so we'll assume Don Kinnison was born about then or a couple years earlier.
Using Ancestry.com, I found a Don E. Kinnison born 1925 living in at Rr 160 Radcliff Ohio at least 1985 through late 1990's.
Another 2002 record shows a Donald Eugene Kinnison born 28 Jun 1925 born in Vinton Co. OH died 28 May 2000 in along term care facility in Jackson Co. OH He died age 74 Certificate # 040604. His SS # was 296-20-1146. His father's surname was Kinnison and his Mother's surname was McDaniel. Education was 8 ( I assume that meant through 8th grade). Certifier was a Physician, name not given.
This Donald Eugene Kinnison sure sounds like your Great Grandfather.
Next I looked at the 1930 census (last census with results on Ancestry.com)for a son Donald who would be about age 5 (born 1925). I found a Robert Kinnison age 50 (b. abt 1880) in Wilkesville, Vinton Co. Ohio. He had a wife Nettie age 42. Donald, his son, was in their home at age 4 years (probably the census was taken before his birthday). Anyway this Donald who likely is your Great Grandfather had the following siblings: Glen age 22, Sanford age 15, Clement age 12, Fay 10, James 8 and Lillian 7/12.
Must run for now. When I get a chance, I'll see if I can find more on Robert Kinnison who likely is your Great, Great Grandfather.