Barnes was born on December 28, 1989, in Riverside, California, the oldest of four children born to Dennis and Stephanie Barnes. Although his mother is Mexican-American, he was raised speaking only English. His maternal uncle, Mike Gallego, played in Major League Baseball (MLB) for the Oakland Athletics. He began playing baseball at a young age. As a shortstop in Little League Baseball, Barnes' nickname was "Hoover", given for his ability to field ground balls.
