Sibling relationships are some of the longest-lasting relationships people experience, providing ample opportunities to build connections across the lifespan. For siblings and people with intellectual and developmental disabilities (I/DD), these connections take on an increased significance as their families age and parents can no longer provide care. This paper presents findings from a qualitative study that addresses the question, “How do siblings support each other after parents no longer can provide care to the person with I/DD?” Findings in this study suggest that siblings with and without disabilities experience reciprocity as a transitive exchange, which occurs through the creation of social capital in their families and community, and that nondisabled siblings mobilize their social capital to provide support to their sibling after parents pass away. Implications for future research as well as policy and practice will be discussed.