It is very hard not to believe that two Darius O'Neil's traipsing around Tennesse at the same time aren't cousins at least. There is a possible Virginia-North Carolina connection referenced below but I have no idea where O'dell's information came from. I suppose its also possible your Darius is the Grandson of the Rev war Darius by first marriage (still family rumor for me) since the rev war fellow's BD of 1764 more than supports the 1791 birth date for your Darius's father Joseph. Marriage to Polly Bracknay (second wife) is 1801 from the pension ap. In “Over the Misty Blue Hills”, her story of Cocke County, Tennessee, Ruth Webb O’dell devotes about a page (p127) to the O’Neils. She talks about seven O’Neil brothers who came to America; five to North Carolina and two to Virginia (no further reference). Then she discusses the Cooke county O’Neils. “The two (brothers) who came to Cooke county before 1816, had large families. Henry, Peggy, Betsy, Mary, Lucindy were the names of one family. The other brother’s children were: Joseph, William, George W., Calvin, Harrison, Darius, Nancy, and Maria. The mother of the last set was a Kitchen from Connecticut. >From these descended the present ones of the name."