['Prolonged, intensive treatment regimens often disrupt families of children with cancer. Siblings are at increased risk for distress, but factors underlying this risk have received limited empirical attention. In this study, the authors examined associations between the family context and sibling distress.', 'Siblings of children with cancer (ages 8-18 years; N = 209) and parents (186 mothers and 70 fathers) completed measures of sibling distress, family functioning, parenting, and parent post-traumatic stress. Associations between sibling distress and each family risk factor were evaluated. Then, family risks were considered simultaneously by calculating cumulative family risk index scores.', 'After controlling for sociodemographic covariates, greater sibling distress was associated with more sibling-reported problems with family functioning and parental psychological control, lower sibling-reported maternal acceptance, and lower paternal self-reported acceptance. When risk factors were considered together, the results supported a quadratic model in which associations between family risk and sibling distress were stronger at higher levels of risk.'] Does cumulative family risk predict sibling adjustment to childhood cancer?