In my opinion: Nero is not Vergil's son, nor is he Sparda's. If Nero is 17 or 18, and Vergil and Dante are around 28-29, there is no way Vergil could be Nero's father because then Vergil would have been 11 or 12 when he impregnated Nero's mother and that is not possilable. Nero is in no way, truly geneticly realated to Sparda. Read my game concept to find out the methods to my madness. It's called anicent runes and it's in the fanfiction section.