I'm not sure that Eurnice and Thankfull were married to the same David.
It does look like though that Thankfull was married to the David, son of William and Lidia Goodale as Thankfull's sister is also married to another one their children. There is a marriage reccord that Thankfull Maynard married David White in Marlboro, New Hampshire 29 Sep 1801 but it does not specify parents. There are also birth records for their children from Lydia in 1801 to Irene in 1816. al attached on familysearch. There is also a town vital records that has David, the son of William and Lydia born 11 or 29 Mar 1777 Bolton, Massachusetts.
This is why I think it was a different david who married Eurnice Shannon. There is a marriage record for 5 Mar 1805 in Nelson, New Hampshire. Eunice is buried next to a David White who's death match this profile and according to his grave was born around 1777, same as the David above. I am guessing because of the birth year, the two Davids were mixed up and have been copied since.
There as also a 3rd David White that I am looking at that has the same profile within the ancestry community who married Nancy Ann Folger.
I do believe they are all connected to the same white family, as I get DNA matches connected to Goodale and Folger descendents.