Abstract Siblings of individuals with neurodevelopmental conditions (NDCs) experience distinct challenges and have unique strengths compared to siblings of individuals without NDCs. The present study examined attributes and aspirations of siblings of individuals with and without neurodevelopmental conditions, and analyzed the association between qualitative responses and quantitative measures of growth mindset, positive and negative valence, and mental health diagnoses. A novel mixed methods thematic analysis was employed to explore the experiences of 166 siblings (75 NDC and 91 controls, aged 14–26, 66.27% female) completing an online survey as part of a larger study on sibling mental health. The overarching theme described The Process of Self‐Actualization and Integration , reflecting the journey siblings undergo in seeking to understand themselves and others amidst psychological challenges. It encompassed three subthemes: Personal Growth and Identity Formation ; Connection and Belonginess ; and Societal Perspective and Global Consciousness . Qualitative responses were analyzed within a Research Domain Criteria (RDoC) framework, and associations between phenomenology and mental health diagnoses examined. NDC siblings had higher negative valence and lower positive valence embedded in their responses, and quantitatively lower self‐reported growth mindset (i.e., beliefs about the capacity for personal growth), compared to control siblings, which correlated with self‐reported mental health diagnoses. Findings suggest clinical practice may focus on optimizing self‐identified strengths and offer opportunities for self‐actualization of hopes and ambitions, while providing support for families to attenuate bioecological factors impacting mental health.

“Broken fragments or a breathtaking mosaic”: A mixed methods study of self‐reported attributes and aspirations of siblings of individuals with and without neurodevelopmental conditions