When Huang Baoying was growing up, her older brother helped look after her, their parents recalled. Huang Bocan would tutor his younger sister at night and help her with her studies, their mother said. To his parents, he was a responsible son whom they trusted to help care for Baoying while they worked long hours. Years later, he would be sentenced to life imprisonment for murdering her. “We never imagined that things could become so serious,” their father said after Bocan, 34, was sentenced on...