Sibling relationships are amongst the most influential relationships in one’s life. Bringing autism spectrum disorder (ASD) into these interactional dynamics has a marked influence on these relationships for both the sibling with ASD and the typically developing siblings. The main aim of this study was to investigate how typically developing adolescents describe their present attitudes towards their sibling with ASD, compared to their attitudes when they were younger. Thirty typically developing adolescents who have siblings with ASD were selected to complete the survey instrument, namely the Modified Lifespan Sibling Relationship Scale (MLSRS). The survey instrument operated on the conceptualisation of attitudes as consisting of three components: affective, cognitive and behavioural. The results indicated that the majority of adolescents have very strong positive feelings towards their sibling (affective component), both at the time of the research and when they were younger. Their beliefs about their siblings and their relationship with them (cognitive component) have become more positive as they became older. Their actual interaction (behavioural component) was, however, found to be significantly lower than their feelings towards their siblings (both as adolescents and as younger children) and their beliefs about their relationships as adolescents. This study highlighted the need for children who develop typically to be taught how to interact effectively with their sibling with ASD and the need for siblings to be provided with age appropriate information about their sibling’s disorder. The results also indicate that although most of the children seemed to be coping well with the extra demands placed on them they would nevertheless still be able to benefit from support groups for siblings of children with ASD.