This article examines families’ involvement in the care and management of people with serious mental illnesses in China, and focuses on how that involvement is shaped by changing psychiatric institutions and law. Drawing on 32 months of fieldwork, I show that familial involvement is primarily characterised by guan [管], which can mean ‘care’ and/or ‘control’, and which commonly invokes a particular cultural ideal of parenting. Tracing how the language and practice of guan circulate between different realms, I argue that a ‘biopolitical paternalism’ has emerged in contemporary China. It reduces patients to carriers and manifestations of biomedical/security risk and legitimises the state’s policy of population management as a form of paternalistic intervention, while displacing certain paternalistic responsibilities, such as hospitalisation and ensuring medication compliance, onto patients’ families. This biopolitical paternalism produces vulnerabilities and unease within families and aggravates health disparities between patients. The analytic of biopolitical paternalism has conceptual efficacy and practical implications beyond mental health.