Background: The impact of having a disabled brother or sister on siblings' psychological well-being and sibling relationships has been the subject of several research studies. However, research which focuses on the relationship between siblings and their autistic brother or sister with an intellectual disability and complex care needs is rare. We explored siblings' views and experiences of their sibling relationship with their autistic brother or sister with complex care needs. Method: Eleven children and early adolescents (4 male/7 female) between the ages of 8 and 14 years took part in semi-structured interviews with questions focussing on their relationship with their autistic brother or sister who had complex care needs. Reflexive thematic analysis was used as a guide to analyse the data. Results: Four themes are presented: positive interactions bring joy, sibling conflict is driven by verbal interactions, behaviours may have different meanings for the sibling, perceptions of change in the sibling relationship. Conclusions: The siblings of autistic brothers and sisters with an intellectual disability and complex care needs described warmth and positivity. Siblings of autistic children, who have complex care needs, deeply valued their interactions with their brother or sister despite reciprocity being on their terms. When autistic brothers and sisters had some functional spoken language, this often changed the context for the siblings relationship; perhaps leading to an increased chance of conflict or perceived negative experiences. These findings highlight the importance of understanding the individual meaning of these sibling relationships.