This paper identifies the health penalty experienced by girls due to having a brother from endogenous sibling gender composition. We propose a girls-to-girls comparison strategy and rule out the confounding effect from the sibship size, birth interval, and birth order. Employing an instrumental variable approach and data from the Chinese Family Panel Studies, we find that girls with a brother are demonstrably shorter and report poorer health. This \"brother\'s penalty\" manifests even prenatally. Alternative explanations, such as birth order disadvantages, are carefully addressed and ruled out. The results hold even after excluding gender-neutral ethnic minorities. This observed penalty is likely attributed to unequal resource allocation within families and potential parental neglect. This penalty is amplified in families with lower income and maternal education, implying resource constraints contribute to gender discrimination. Our findings highlight the importance of addressing intrafamily gender bias for ensuring equal opportunities and health outcomes. Clinical trial registration: Not applicable.

暂无摘要。

After more than three decades of implementation, China\'s one-child policy has generated a large number of only children. Although extensive research has documented the developmental outcomes of being an only child, research on the parent-child relational quality of the only child is somewhat limited. Using China Education Panel Survey (2014), this study examined whether the only child status was associated with parent-child relationships among Chinese junior high school students. It further explored whether children\'s gender moderated the association between the only child status and parent-child relationships. Two-level ordered logit models suggested that only children were more likely to report a close relationship with their mothers and fathers compared to children from multiple-child families (including two-child families). Taking birth order into consideration, we found that, only children were more likely to have close parent-child relationships than firstborns, whereas no significant differences were found between only children and lastborns. Interaction analyses further suggested that the only child advantages were gender-specific: the positive effects of the only child status were stronger for daughters than for sons, that is, daughters benefited more from being only children. Our findings highlight the importance of considering children\'s gender and birth order in exploring the only child effects in the Chinese context. Additional analyses about sibling-gender composition indicated female children were more likely to be disadvantaged with the presence of younger brothers, whereas male children benefited more from having older sisters. This reveals that the son preference culture is still deep-rooted in the Chinese multiple-child families.