My grandmother was Eunice Lee Coppock, sister to your Cora. According to information I once had, Matthew's father was a Dr John Taliaferro, I probably have a little more on him if I can locate it. I have had contact with descendants of Lily Fern and one of the girls that married Allens and they may have more.
I have pictures of George & Polly, together and by themselves, pictures of Cora and Matthew. In fact I have pictures of all of George and Polly's children in a group photo and come to think of it Matthew's mother is in the photo and she was Ruth Ann, if my memory is correct the spelling was slightly different than what you have but it is Matt's mother.
I have the Coppock and Seaton as far back as it goes with any documentation and I have some decendancy data on all George's kids and would welcome anything on your branch of Matt and Cora's kids. Feel free to contact me directly at email@example.com Take care.
Gary Hawley A Gr-Grandson of George Washington Right Coppock and Polly Ann Seaton BTW George's tombstone and all his military records has his name Right although I am sure there is a Wright in our background.