Brother, Sister, Where Art Thou? Rethinking the Role of Siblings in Child Development Attachment Research: A Narrative Review and Original Findings from the London Parent-Child Project

ABSTRACT Sibling bonds are often central in children’s everyday lives, but they remain underrepresented in developmental and clinical research. This article reviews the developmental and clinical significance of sibling relationships through the lens of attachment theory and presents some original research on siblings that were participants in the London Parent-Child Project. We examine how sibling relationships contribute to children’s social, cognitive, and emotional development. We highlight the bidirectional and ambivalent nature of sibling interactions, the moderating effects of parental differential treatment, and the predictive role of attachment representations within the sibling subsystem. We further explore cross-cultural perspectives, sibling dynamics in adoptive placements, and findings from the Friends and Family Interview administered to siblings.