Upon researching your letter, I was a little surprised that Capt. Sevier's grave was marked. I was under the impression it had never been found.
Regarding your 6th great grandmother Kezeiah, I believe that her mother, Susannah Nichols may also be a relative of my wife. I haven't researched all the branches yet.
You are right about no one mentioning Kezeiah's ancestry. I think its great. Welcome to the family!