Intra-familial sexualized violence by siblings remains a largely untouched taboo subject in Germany. However, many professionals in education and therapy work daily with boys and girls who have committed sexualized violence against their siblings or with siblings affected by sexualized violence and their families. In this practical handbook, experts from both practice and academia compile their diverse experiences from working with sexually aggressive boys and girls for the first time. Based on current international research findings and in some cases decades of practical experience, the following topics are discussed: tabooization, differentiation between doctor play and sexualized assault, critical examination of an admission of guilt as a prerequisite for receiving help, frequency, and functions.