This study examined factors influencing involvement of siblings of individuals with developmental disabilities in future planning and their expectation of future caregiving. The sample consisted of 139 adult siblings recruited from an online sibling list and a sibling conference. Results indicated that few families made plans or involved siblings in the planning. Siblings who were most involved in future planning were older, more involved in disability activities, and provided more support to their sibling with disabilities. About 38% of siblings expected to be primary caregivers and were more likely to expect this role if the sibling with a disability lived closer and was female, had more sibling contact, provided them with more support, and felt greater caregiving satisfaction. Major support needs of siblings were for support groups, workshops–training on how to assume caregiving responsibility, financial support, and printed material on making future plans.