Confront abuser

Hi all, wondering about what to do here. Maybe one of you had a similar experience. I was abused by a sibling when I was 12. Of course made me promise that I would not tell anyone. In the years after that we basically acted like nothing ever happened. Only my therapist and a few close people know. But I feel like sharing it with for example my other siblings could help me processing it, get a burden of my shoulder by not having to keep it a secret.

I have the feeling I have to talk to my abuser first, although we hardly have any contact since 20 years or so. Something like it feels like a betrayal if I would share this secret without giving them the option to acknowledge and maybe even apologize first. I also think it may shake up the already fragile relationships in my family, and my old parents’ mental health. So basically I’m afraid of the consequences of bringing this out in the open.

Does any of you have any experience with a similar situation?