 Jackson Holiday, but this Jackson seems to be getting it done maybe before Jackson Holiday. I think Jackson Holiday is a year younger than him. Yeah, he's 21. Jackson Merrill's 21. He graduated from Severna Park High School three years ago. Three years ago, he was playing in the state championship game, and now he's in the All-Star game. These are the only people who have played in the All-Star game at a younger age, apparently. Mike Trout, Miguel Cabrera, Alex Rodriguez, Ivan Rodriguez, and Ken Griffey Jr.