Background: 'Harmful sexual sibling behavior' is a term used in this study to refer to childhood sexual behaviors, including abuse (SSA), that are inconsistent with the category of age-appropriate curiosity. Although SSA may be the most prevalent and longest-lasting form of intrafamilial sexual abuse, it is the least reported, studied, and treated.

Objective: This study aims to deepen our understanding of the sexual characteristics and dynamics of such behavior, as perceived by those involved.

Participants and setting: Twenty adults from the Orthodox community in Israel, who experienced sexual interactions with one or more of their siblings, were recruited as participants.

Methods: This qualitative, constructivist, grounded-theory study was based on semi-structured interviews with 20 adults.

Results: Four types of sexual dynamics were revealed: an "abusive dynamic," "mutual relations," "sexual routine," and "incidental," with the latter stemming from a new understanding that deepens our knowledge of the subject. The participants discussed the broad, long-term consequences and life-long psychological implications of each dynamic and the coexistence of these dynamics. The results also reveal two cultural dimensions of the participants' perception of the sexual acts: "lack of sexual knowledge" and "the perception that all religious prohibitions are of equal severity."

Conclusions: The findings highlight the importance of adapting interventions to the siblings' perceptions and avoiding treatment that exacerbates their complex situation. We employ the concepts of dynamics and dimension in describing the phenomenon rather than continuum. The study also highlights the importance of understanding relevant religious-cultural factors.