Whilst the majority of sibling relationships are generally benign in providing an additional secure attachment figure and source of comfort in which they can grow and flour- ish, some are highly competitive, full of envy, rivalry, and resentment, which can lead to physical and sexual violence. It is estimated that sibling sexual abuse (SSA) is three to four times more common than adult to child sexual abuse (CSA) in the family. Lack of knowl- edge, research, and discourse on psychosexual development in children and the nature of SSA has led both parents, child protection professionals, and clinicians to normalise sexual interactions between siblings, and to minimise these as less harmful than generational CSA. To ensure that sibling sexual interactions, their impact, and long-term effects are fully understood, it is essential that parents and practitioners understand what constitutes harmful sexual behaviour (HSB) between siblings and be able to distinguish between developmentally typical sexual behaviour and developmentally atypical sexual behaviour in children. In recognising the nature, concomitant risk factors, impact, and long-term effects of SSA, parents and professionals will be more able to bear witness to the lived experience of SSA and facilitate the healing process.