Drummer MckNasty - real name Joshua McKenzie - is the sibling of singer Labrinth, who is already signed by Simon Cowell's Syco record label.
McNasty tried out for the judges in London this week and sailed through to the next round.
But insiders have claimed that Simon already knew the musician.
"It looked like someone had been pulling strings. Simon went to ask Joshua a question — he said, ‘Do you have any... tell me something interesting about you.'," a source told The Sun today. “It was as though Simon was going to ask if he had any famous relatives, that he already knew who he was.”
Joshua told the judges at the London Palladium: “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.”
A spokesperson for the show insisted: "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.”
The Britain's Got Talent 2013 auditions in London conclude today before moving to Glasgow at the weekend.