Since posting the query about John Seaver b. @1770, I have learned that the John Seaver 1795-1835 was the s/o William Se(a)ver(s) of southwest VA.
There are many very strong indications that William was a brother (or a very close relative) of the John Seaver b.@1770, of Jacob Seaver b. 1773, and of Elizabeth Seaver Lamar--all said to be children of Henry & Elizabeth Seaver.