Complex sentence: At the age of 15, Larry moved out of Shelby and finished his high school career at Big Sky High School in Missoula, living with his older brother Bernie, who became the legal guardian of Larry.
Split into simpler sentences: At the age of 15, Larry moved out of Shelby and finished his high school career at Big Sky High School in Missoula. During this time he lived with his older brother Bernie, who became the legal guardian of Larry.