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...
Our bodies are designed to like sex and abusers are often very good at using that against their victims. They know how to make our bodies override our minds - this makes the abused believe they were complicit in, or even responsible for, the abuse.
This is very good for the abuser because he can shift some or all of his guilt on to you and you are less likely to tell anyone if you feel (partly) responsible.
You were used and manipulated, you were a child and he knew what he was doing. He made it seem like you had a choice.
You didn't. You did nothing wrong.
By the way - I think you're very brave raising this. I have only ever discussed this aspect with my therapist.