The currently-unidentified hopeful appeared in front of judges Simon Cowell, LA Reid, Britney Spears and Demi Lovato at the Greensboro Coliseum in North Carolina.
"This guy came on and told the judges a story about how his grandmother was in the movies and after they'd been talking for a few minutes, they finally realised that Ray Charles was his grandfather," an insider told The Hollywood Reporter. "The judges were massively surprised."
Charles had 12 children, and was grandfather to at least 21 grandchildren at the time of his death in 2004.
Kiss musician Gene Simmons was given a surprise when his daughter Sophie Simmons auditioned for The X Factor in San Francisco on Father's Day, while Jim Carrey's daughter Jane tried out for the most recent season of American Idol.
The X Factor USA's second season will debut this September on Fox.