The two men helping him to leave China were Tang Zhishun, 40, an engineer from Beijing, and Xing Qingxian, 49, a human rights activist in the southwest city of Chengdu, Zhou said. “We’re really worried now. He’s just a 16-year-old boy,” said Zhou, who lives in San Francisco. “We know that the intention is to use him as a hostage against his parents, both of them famous human rights defenders, in particular Wang Yu. She has been very courageous, outspoken, one of the best human rights lawyers in China — she was arrested exactly for that reason.