See what a child psychologist suggests. Many children do not recognise or understand the harm they have experienced until they are older and know more about sex and relationships When i was around six, my older brother (who was around nine or 10 at the time) used to get me to play a game called ‘naughty exercises’ with him.
Sister & brother seeing each other for the first time! - YouTube
Your sister will grow up to understand that you are a good brother and you had no intention of having sex with her, and having an erection did not mean you wanted to have sex with her.
I think that if she wants to be nude and natural she should do it in the bedroom with the door closed so nobody sees her except our younger sister, with whom she shares a room.
Unless you need help in the bathroom from your parents, or if you are at the doctor’s office getting a physical exam, no one should touch or see your genitals but you If someone is asking about your private parts, talking to you about theirs, or if anyone ever makes you feel uncomfortable, it is important to talk to a trusted adult. Sibling sexual behaviour can be difficult to understand and assess
