So, towards the end of the game, when you're opening the vault, Vergil and Dante got into a discussion.
Essentially, Vergil taught himself his computer skills when he was a kid, since he felt there was something more to his life. Both him and Dante felt this way because of how their pasts were hidden from them, but there was an inkling there. Vergil channeled that into his computer work, while Dante..."Killing demons and getting laid. But...that computer stuff is good, too."
So as it seems, both brothers knew there was more to their lives, but they couldn't quite figure out what. They kept themselves from becoming too frustrated about it by pouring themselves over their respective...uh..."hobbies." This is probably what began to spark Vergil looking deeper into his past when he got older.