Hi Nancy, I saw your reply to this post and thought I would take a look.
When your grandfather married in Caldwell County, Missouri, Frank was described as being from Nettleton, Missouri. there was a Buxton family very close by in New York, Missouri, with parents John Wylie Buxton (b. April 1825 in Pennsylvania) and Nancy Buxton (b. March 1827 in Pennsylvania)
The individuals are the correct age to be Frank's parents and are consistent with the parents of Frank being reported as born in Pennsylvania in the later censuses. Additionally, Frank's first son was John W Buxton, whose middle initial is consistent with John above, and could possibly be named after him.
Unfortunately, none of the censuses for John and Nancy seem to include Frank, and I would especially expect the 1870 to do so.