There is a marriage in 1963, with son born the same year.
That was confirmed by a local who knew him and the family.
Considering the dates, 1942 is reasonable in being 21 when married.
If the marriage certificate says he was 21, that could explain the source.
It would help to know the accuracy of 1942.
Once I receive a response from FamilySearch I will post it, though I am not holding out much hope.