Ok so this is just a random theory that's probably way off but here's how it goes.
WARNING MAJOR SPOILERS FOR DmC, VDF, DMC3
Once Vergil is killed by dante and goes to hell (VDF story) he kills hollow Dante and takes his amulet. This kills real Dante and scientists are trying to bring him back to life (Because he's nephillim) meanwhile Vergil is trying to combine the amulets to unleash spardas true power. Vergils plan goes wrong and he forgets who he is. Same thing happens to dante when he is brought back to life by his parents. (because he's the favorite) They figure out the truth of their father but the truth of their mother is hidden to protect them being as big of a target as thet were before. Their mother is told to be a human in a fake story Dante and Vergil are told. Dante trys to protect the world from demons by opening a bussiness called Devil May Cry. While Vergil on the other hand is trying to unleash Sparda's Power.
Shut up i know im wrong.