This is a really interesting & surprising finding.Do you know what sort of evidence supports it?
The only reference I've found that connects a Fanny Franklin with a John Keeling in Henry Co, VA is in a deed of gift from Joseph Keeling to his son John Alexander Keeling and daughter-in-law Fanny Alexander Franklin(g) in 1783 (Henry Co, VA Deed Book II, p 392-393.)I don't know if this is meant to imply that her maiden name was Franklin, but it seems like her married name should be Keeling as of 1783.
The marriage bond for Wilson Rea and Fanny Franklin in 1796 doesn't name her as Mrs. Fanny Keeling, which is what I would expect if she were widowed/divorced from John Keeling.I have also seen Wilson's wife named as Fanny Anne Franklin, not Fanny Alexander Franklin.
In any case, John Keeling's wife, Fanny, couldn't have been born much after 1763, and perhaps earlier.Wilson & Fanny Rea's last child, Wilson A Rea, was b. 1820, which would have made her age 55+ at the time of birth.