Background: It is becoming more common for siblings to fulfill a caregiving role for their brother or sister, particularly because people with intellectual/developmental disabilities (IDD) are often living longer and outliving their parents. However, most of what we know about siblings of people with IDD is based on research with children, and limited studies on the adult sibling experiences in Canada have been published. To meet the support needs of Canadian adult siblings, "The Sibling Collaborative", a grass‐roots initiative, conducted a needs assessment.