Hi.I saw your message when I did a “daily search” for the Averill surname, and I decided to see if I could find anything to help you in the Averell/Averill/Avery Family Genealogy book by Clara A. Avery.
Matthew Riggs and Molly (also known as Polly) Averill are mentioned on page 485 of the Genealogy.It says that Molly (or Polly), “was a noted beauty, with a clever mind.”It also says that, “she was married when not quite fifteen years of age to Matthew Riggs, who was a reputed scholar.A Latin Grammar by him was for some time in general use.”
Six children are listed for Matthew and Molly, but no dates are given.They are Edward, Mary Ann (married McCune), Abigail (married Maxwell), Thomas Jefferson, Elvira (married first Seeley and married second John Mitchell), and Eleanor.
No further information is given about Matthew Riggs, but the following quote about Molly is interesting.“Mrs. Riggs moved to Evansville, Ind. some years after her marriage, and died there in 1850, when about 70 years of age; but she was so youthful in appearance that she was thought to be many years younger.”
I hope this helps you find the information you’re looking for.Good luck!