Background <p>Family health is an important variable that links internal and external resources at the family level, exerting significant effects on individual health. However, there remains a lack of empirical evidence regarding its potential to mitigate health disparities. Therefore, the present study aimed to explore the effect of family health on income-related health disparity in China and analyze the heterogeneous effects of different dimensions of family health across different sub-populations.</p> Methods <p>Using nationally representative data from the 2023–2024 Psychology and Behavior Investigation of Chinese Residents [n = 49,885], we employed health-related quality of life (HRQoL) as a proxy variable for individual health and applied the recentered influence function-index-ordinary least squares model to explore the contributions of family health and its four dimensions to the disparity in HRQoL.</p> Results <p>Our findings showed that family health had a significantly negative association with the concentration index of health utility index (UI; β = -0.0002, P &lt; 0.05) and EuroQol Visual Analogue Scale (EQ-VAS; β = -0.0006, P &lt; 0.01). Family social or emotional support was negatively associated with EQ-VAS disparity, and family external social support significantly contributed to lower UI disparity. However, family health resources were positively associated with the disparity in UI and EQ-VAS. Heterogeneity analysis revealed more pronounced effects of family health in mitigating health disparity among females, young populations, and urban residents.</p> Conclusions <p>This study emphasizes the importance of alleviating health disparities through family health improvement. In addition, the study findings demonstrate the necessity of reshaping resource allocation at the family level—balancing external supply and internal equity of families among different subgroups—and accelerating the distribution of high-quality medical resources to economically disadvantaged areas.</p>