Reeves was born with the name of George Keefer Brewer in Woolstock, Iowa, U.S., son of Don Brewer and Helen Lescher. He moved to California at a young age with his mother Helen. Reeves started acting in high school and then continued to serve on student productions. In 1943, 17 months after the attack on Pearl Harbor, Reeves enrolled in aviation until the end of World War II, putting his acting career on hold. 