Claim: Gregor Clegane's younger brother is also known as The Hound.
Evidence: Ser Gregor Clegane is a huge knight and the elder brother of Sandor Clegane.
Sandor Clegane , nicknamed The Hound , is a fictional character in the A Song of Ice and Fire series of fantasy novels by American author George R. R. Martin , and its television adaptation Game of Thrones.