AbstractBackgroundAdult siblings are important in the lives of individuals with profound intellectual disabilities, especially as parents age. However, little is known about the roles they assume.MethodWe examined these roles among 58 participants from the Netherlands, who completed an online questionnaire.ResultsMost participants (89.7%) assumed multiple roles, and the majority were content with their roles. Between 7% and 58% indicated that they were the only individuals providing a certain role. Shared roles primarily involved healthcare professionals, other siblings, and parents. Almost half the participants (48.2%) assigned higher scores for the amount of support provided than for the experienced burden.ConclusionsAdult siblings often assume multiple roles. The shared roles emphasise the importance of collaboration.