[FrankieS]

Bon soir!

In the end it will remain a philosophy I guess.
I think the birth certificate is the valid document
and also on the military file there could be an error, given
that also the birth certificate shows this father/son discrepancy
which shows in the end:
a) that even officials can err (and military officials maybe too? ;-))
b) it's a good thing to be as accurate as possible for your project, but maybe this issue not so important, could however potentially change the order of this person in an alphabetical index.

best wishes,
FrankieS