Well like I've said in the past, whatever way you look at it Capcom really screw us around with plotholes and the like.
I mean c'mon. On one hand we have a guy (Bingo) who worked for Capcom, leave. And he goes and writes a novel. And in it he 'reveals' that Nero is indeed Vergil's son. And then on the other hand, in the Devil May Cry 4 Instruction Manual it states that Nero was infected (So his arm is like a demonic infection). And then in the game itself we have other such hints that Nero is 'a descendant' of Sparda and he has 'inherited' his blood and such things like this.
Which one is it Capcom? Because I just saw three theories you've put out there for your own character. Maybe you should probably know who you're character truly is before you try and sell him off to the World to cash in a profit.
This is more than likely why the majority of fans still hold somewhat dislike for Nero. Not because of who he is. For the fact that we can't hate him for how he came to be, because we don't even know how he came to be. Nero to me was an injection to the franchise to try and stop itself from falling apart. And yeah it may of worked for a little while, but honestly it's still not so great now. Don't leave fans in the dark. You're not just confusing one person, you're confusing potential millions. And personally to me, that's quite disrespectful.
If they have any decency towards the people they are trying to sell the game to, they would justify their storyline. I look forward to having Nero's origins finally put to rest once and for all.
And last but definitely not least, heed these words Capcom. Making money is about selling your product. Know what you're selling first, it helps