From Halopedia, the Halo wiki
Gabriel was born to a pair of respected UNSC Army officers. He moved to New Phoenix in 2540 at the age of six, after his grandfather convinced his mother that he should know her homeworld. Gabriel loved his maternal grandparents, but resented Earth because he felt it was too old and too built up. After Thorne lost his parents at the age of eight, he was raised by his grandparents. His grandmother taught him how to play the violin and hoped that he would follow in her footsteps. His grandfather died in 2553 and Thorne last saw his grandmother at his funeral. Thorne's grandmother was composed along with the rest of New Phoenix's population when the Ur-Didact fired the Composer upon the city.
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