Greg was born in Indianapolis where he lived a happy life until his mom married George Diablo, a wealthy businessman. However, George revealed his true color when he went violent on Greg. He would beat Greg whenever Greg's mom was out. Later, George divorced Greg's mom. After a week later, he was muted due to his abuse under unknown circumstances. Later, he meets a new kid named Adrian Hakai and Abigail Chaste. They slowly (very slowly) became friends. Later, Greg and the kid were sent to a camp called Camp Half-Blood to be heroes. There, Greg became friends with the kids from the Wind Cabins who helped him because he was mute. He encountered a hellhound when he was thirteen.
He was saved by a group of demigod kids who decided to go back to their hometowns to meet their parents for a while. The demigods told him he was son of a god. The satyr friend of the demigods later sent him to Camp. He is now free from the abuse of his stepfather.