The drummer wowed the judges at the weekend with his performance, which including playing and DJing at the same time.
But MckNasty - real name Joshua McKenzie - is the brother of rapper Labrinth, signed to Simon Cowell's music label.
Joshua told the judges at the London Palladium during his audition at the start of the year: “I’m always at the back and I want to be at the front.
"My brother is Labrinth, he is pretty cool. I like the fact that I have to chase him.”
After his audition, Simon told him: “I think you’re brother’s going to be really proud of you, I really do."
Speaking after his audition aired on Saturday night, Joshua claimed he wasn't concerned about there being any fix claims.
He said: “I wasn’t worried people would think it was a fix. I’ve only ever seen Simon on TV. I’ve never met him. My brother also didn’t know I’d entered.”
A spokesperson for the show commented previously: "To claim that he has been given any advantage is ridiculous and totally untrue. He wowed the audience and went through on his own merits.”