You are correct that there were two Willis Gwaltney families of about the same age in Isle of Wight & Surry counties. I believe that your ancestor is a son of Richard (abt. 1779-1815) & Martha Gwaltney of Isle of Wight & Surry counties; and grandson of Patrick (abt. 1750-1802) & Martha Gwaltney of Isle of Wight co.
The other Willis Gwaltney (about 1781-1820), who married Elizabeth Edwards in Dec. 1804, was of Surry county, and was the son of William (died before 2/26/1811) & Elizabeth Wombwell (d. before 3/27/1837) Gwaltney. This Willis also had a son Willis (about 1813-56), who married Winifred Moody in 1835, and who lived in Isle of Wight county.
None of the above are descendants of Thomas Gwaltney (about 1732-98) by either of his two wives. He had only daughters by his first wife, Elizabeth Clarke, and two sons, Thomas P. and Ludwell by Sarah, his second wife.
If you would like to contact me directly, I can send you family group sheets for each of these men.
Sincerely,
Anne Gwaltney
agwalt@earthlink.net