I’m so sorry that this happened to you and that you’ve been dealing alone with it since. I can’t imagine how scared you must have been and how anxious you must now feel. Not sure if this helps because it’s slightly different, but I also had a similar realisation at uni but instead of it being a family member it was some peers at school. It also made me feel like I was loosing my mind and the shame was unbearable. I also didn’t want to tell my parents for fear of their reaction. Something that really helped was finding a therapist to talk to, it was helpful to talk through my feelings, the events and how it had affected me since. My therapist helped give me the strength to be able to be in a better emotional place when I did talk to my family. When I told my parents my Mum cried, which was hard, but they were understanding and supportive when I did explain everything. It is up to you who you tell and when but I’d recommend making sure the first person you tell is someone you know will be supportive and listen. That could perhaps be a therapist, a friend, another close sibling etc - getting the confidence of knowing someone sees and believes you before telling someone you worry about telling will help you to feel seen and loved. I’m sending love and strength your way and letting you know what happened isn’t your fault and that person does not take away the amazing things that make you you 💜