I am also a descendent of Jackson & Marthay Harwell. Just to make sure we are talking about the same people, 'my' Jackson was born 25 Jul 1773 Brunswick Va. He was married three times. Wife #1 was Marthay "Patsy' Fretwell (1780-1808), wife #2 ? Thweat. wife #3 Rhoda Watts who married a Starr, then a Patrick then Jackson Harwell. They married in 1837. Most of this info is from the family bible which is on file at the Ga. Archives. the other source is described below.
Another wonderful source of info on Jacson is the book titled "The Diary of Dolly Lunt Burge, 1848-1879, edited by Christine Jacobson Carter" Dolly as a neighbor of Jackson's in his old age. She records conversations with him and visits to him. Also his death & burial The entire diary gives a real sense of place & time - especially when Sherman came through.