Let me lay out my "evidence" as it stands:
First of all, the Jackson family bible lists a "Barbara Jackson" who died 20 Oct. 1821. This is the only woman listed as "Jackson" who wasn't listed as a child of Reuben in the "births" and this timing works with both James Madison Jackson's 1819 birth and Reuben's 1822 remarriage. So I started there: what if she were his first wife?
Secondly, I wondered about the birth of William Harpole b. 1 December 1800 appearing in the Jackson family bible. His lineage is clear and established: he is brother to the John Harpole who was Captain of Reuben Jackson's regiment and this whole family, too, moved to Obion County, TN. His parents were Solomon and Anna Christina Dice Harpole. Why was he there? So, guess No. 2: this boy could have been Reuben Jackson's first wife's nephew.
So I began looking into the Harpole and Dice families, which are well documented on the internet. No luck with the Harpoles, but the Dices had a plum: Anna Christina had a sister named Barbara who married a "Joseph Jackson" in 1797 in Pendleton Co., (W)VA. But there was a funny note attached to some peoples notes on this marriage: he may have been named "Reuben Jackson". None of these people list any sources for their materials, so I have wrote them for clarification. I received no responses.
Later, I found this gem on ancestry.com message boards:
>Reuben Jackson - late 1700s-early 1800s
>Author: Julia Clay
>Surnames: Dice, Jackson
>Reuben Jackson married unknown Dice. Thier daughter Phoebe
>Deborah was born near Staunton VA in 1802 and raised in Wilson
>Co TN. If you have information on this family please contact
This Phoebe Jackson married Hugh Curlin (appears in Wilson Co. 1820 census), his line, too, is well-documented and though he moved on to Texas, his brothers all ended up in Obion Co., TN.
Further research has comfortably linked Phoebe Jackson Curlin and Reuben Jackson of Wilson Co., TN.
The Curlin's and Harpole's both migrated to Obion County, Tennessee at the same time that Reuben did.
I have since been contacted by another family member whose family had recorded their relationship with Phoebe Jackson Curlin - they descend from Reuben's son Jesse Harper Jackson - the 'Harper' seeming to be another possible connection with the Dice family, since Anna Christina's mother was Catherine Herber/Harper.
There is my evidence in a nutshell.
Please see Experience's Children if you would like to see more.