With enactment of the universal two-child policy in China in 2016, the two-child family will replace the one-child family as the main family form. In this study we examined the contribution of sibling relationship quality in shaping the mental health of Chinese children in a two-child family. Parents (N = 280) reported the quality of their children's sibling relationship, and their firstborn's problematic and prosocial behavior, and temperament. Parents' marital satisfaction and coparenting were also assessed. The results showed that after we had controlled for the child characteristics of age...
