I played against him when he was 16
He was a monster compared to everyone, but he was born in Belgium so it's safe to say that it's nearly impossible that they fucked up his birthday. It's probably just his African genes.
Although it's a known fact that players coming directly from Africa or other places where there are major administrative problems often have wrong information. I've seen a lot of young African players in the youth divisions beasting it up because of their physique and when they're + - 18 years old they seem average or bad. Lukaku is not one of them, he's really born in '93.