Marvin Bagley III was born in 1999 in Tempe, Arizona. He is the son of Marvin Bagley Jr. and Tracy Bagley and has two brothers. His father played college football at North Carolina A&T and went on to play professionally in the Arena Football League. Bagley's grandfather, Joe Caldwell, played six seasons in the NBA from 1964-70 and five seasons in the American Basketball Association from 1970-75. Caldwell is one of 20 players to make an All-Star team in both the NBA and ABA, and he won a gold medal as a member of Team USA at the 1964 Summer Olympics in Japan. Bagley III played high school ball first at Corona del Sol in Tempe as a freshman, then at Hillcrest Prep Academy in Phoenix as a sophomore. At Hillcrest, Bagley was teammates with fellow NBA big man Deandre Ayton. He transferred again, this time to Sierra Canyon School in Chatsworth, California, which cost him a year of eligibility. Bagley averaged 24.9 points and 10.1 rebounds per game during his 2016-17 season at Sierra Canyon. Bagley won the 2017 Gatorade California Player of the Year and John R. Wooden CIF Southern Section Player of the Year awards while maintaining a 3.4 grade-point average. Bagley loves to write and record music. While living in Los Angeles, he volunteered at Hoops with Heart, a non-profit benefiting underprivileged youth. Fans can follow him on Twitter (@MB3FIVE) and Instagram (mb3five).