Background: With an international policy trend to close residential institutions, adults with intellectual disabilities are more likely to live in ordinary localities. However, this does not always equate with engagement, leading to forming new relationships and having a sense of connection to place. Social inclusion in neighbourhoods involves a complex interplay of facilitators and barriers. The role of nondisabled adult siblings as connectors for their sister/brother's social inclusion in their locality has received little research attention. This study explores the experiences of nondisabled siblings of offering support for local engagement and siblings with intellectual disability of being supported by their brothers/sisters. Methods: A multiple dyad case study methodology examined the experiences of 16 participants, made up of eight sibling pairs. Adults with moderate intellectual disability living in a range of neighbourhood types and their nominated sibling formed a self-selecting sample. Each dyad took part in a series of three (individual and joint) interviews. Qualitative data were analysed using reflexive thematic analysis in a four-stage process that included individual, dyad and cross-case analysis. Findings: Five themes were interpreted to explicate wide-ranging experiences of the role of nondisabled siblings in supporting their brother/sister to be socially included in their locality, including the sibling role as shaped by the family context: the influence of push and pull factors and the influence of service providers on sibling engagement. Themes also reveal siblings' intentional and unintentional support for social inclusion and a range of factors that foster or hinder local engagement. Conclusions: The role of adult siblings in supporting engagement and as local connectors has potential as a resource that will contribute to the social inclusion in neighbourhoods of adults with intellectual disabilities. However, a range of factors exist that influence the nature of their involvement. Implications for practice and further research are considered.