Well think god for my sources. I have more info on this case with Vergil's place in the 4th conclusion of the Devil May Cry series.

Nero was brain washed into thinking dante killed his parent's when he was little. Nero blinded by anger sit out to find Dante , but when Dante said that he would never kill a Human being and swore on it Nero found out that there was two sons of sparda and that Vergil must of killed them. Dante found out that Vergil was hiding out in a Castle in an Artic wastland. The two devil hunters sit out to the Castle and found Vergil in a Throne room and the final clash of the Sons of Sparda begins from there.