The relationships between neurotypical (NT) children and their sibling with autism spectrum disorder (ASD) can be complex and lead to stress and strained relationships. Existing theories help us understand the relationships of children with ASD and their caregivers, but we have limited knowledge about the experiences of NT siblings. To fill this gap, we conducted a theory-generating meta-synthesis related to the experiences of individuals who have a sibling with ASD. Our findings produce a new theory that illustrates the various factors that impact these relationships (e.g., characteristics of individual with ASD, the family, and NT sibling) and influence adaptation for NT siblings of children with ASD. Implications for practice, limitations, and future research directions are discussed.