I don't have any factual info, but just feel like your Mary Polly had a sister named Phoebe Riggs and a brother named Clisby, borned about 1769 in Tn.as my passed down stories go! MY tales said her father was Dr. Asa Riggs . Phoebe married Frazier Brindley ca 1794 ,as thier first child, Asa Riggs Brindley was born in Jeff. Co. Tn, in 1795. They lived in Franklin Co, GA in 1801 and a Bethuel Riggs lived near. He was a traveling Preacher Don't know what his relation was.I have not been able to find any thing on this Phoebe or Asa!!! Perhaps his other name was Rueben!???