Wife of Henry FitzRoy (?) - Circa Birth Years

Considering that we don't even know who she was, I can't see how that birth date can be valid. It's probably somebody's (bad) guess, preserved as "tradition".

Imho, since my understanding is that the mother of his children is completely unknown, there should be no birthdate entered for her.

And likewise, since none of the birthdates are known for any of his children, those dates should also be left out.

Doing it that way would eliminate the inconsistency.