Incest Survivors Support Group
Incest refers to any sexual activity between closely related persons that is illegal or socially taboo. Consensual adult incest is very rare. Incest between adults and prepubescent or adolescent children is a form of child sexual abuse that has been shown to be one of the most extreme forms of childhood trauma. If you or a loved one is a survivor of incest, join the group...

You did nothing wrong, there was nothing you could do, the shame is all theirs.
Take your time in processing this and be kind to yourself.
Processing is hard. You are not alone.