Sun was born in Yan'an, Sha'anxi, People's Republic of China, shortly after the Great Leap Forward, in a wealthy family of diplomats from the Chinese Communist Party. He was very interested in politics, and often traveled with his parents. In 1974, Sun was asked to remain in Yan'an while his parents travelled to San Francisco. Eight days later, he received news that his parents had been carjacked and shot. Furious, he took up the pseudonym Guilherme Leong and boarded a train south to Macau, hoping to make a living outside the chaos of the Cultural Revolution. He was not questioned because he was highly ranked in the communist party and was able to pass for a southerner.