Hello,
I have a transcription of the David Nelson letter but I am unable to verify his description of Tirzah's family (i.e. there are no Knight families in Hartford CT or VT that match his description that ALSO have a daughter Tirzah.) I have also looked for the surnames of Wright, White, Knights, etc in case there was poor penmanship in his letter (unlikely, since he was a school teacher!) or maybe a transcription error. Nothing checks out, so as a result I am at a brick wall with Tirzah.

I have also tried to obtain death certificates for all of Simeon and Tirzah's children. Only 2 lived long enough in their locales to have death certificates and the only one I can get has the father's name as Simeon Williams but the mother's name is blank.