There is growing recognition of the importance of mental health among children and youth and impacts on the affected individuals. However, little is understood about how the mental health experiences of children affect their siblings and parents. In this paper, we study the intrafamily effects of new diagnoses of childhood depression and anxiety. Using a decade of detailed claims from a large U.S. health insurer, we examine outcomes including overall physical and mental health and health care consumption, as well as a number of specific conditions. We exploit the conditionally random timing of mental health events to identify causal relationships and mechanisms.