This is the winner of Ori and the Blind Forest art contest, which could be seen at the end of credit screen after you finish the whole game. Didn't expect no one have ever uploaded this before.
Vergil would have been about 19 when Nero was born. Assuming the woman involved was human, he was probably 18 when they did the deed. And who knows exactly when they met and started their relationship, whatever kind of relationship that was.
Including the tag for the CMoH because the artist has (correctly) placed it in its proper place on Johnston's ribbon bar.
Interestingly, this also serves to imply that the MoH Johnston carries was indeed awarded to her, rather than being a reference to the one awarded to LCdr Evans.