
I haven't talked to my son but feel if my daughter-in-law does nothing to try to prevent the voyeurism, he should know. The girl is 12. Am I overly concerned? She still does it but is more careful about getting caught doing it. Thank you.
Given your daughter-in-law's belief that there's nothing wrong with her daughter's voyeurism, you may find yourself in the middle of a rather uncomfortable argument between your son and his wife. If your son also feels that letting his stepdaughter watch them have sex is a healthy activity, then all you can do is attempt to persuade him otherwise, using reasoning and logic and if you wish, the strong recommendations of a professional (me and everyone else I know in the mental health profession). If they both agree that there's nothing wrong with their daughter watching them have sex, I am concerned for how your granddaughter is being parented.
In any event, this is your house and you have every right to demand to be comfortable there. I hope for this girl's sake that your son and his wife handle this situation with sensitivity and empathy. Do not accept a continuation of this rooming arrangement or a promise from your granddaughter that she will stop her peeking through the vent. It's too tough a promise to ask her to keep. Demand the changes now and hope for and support the delicate, non-shaming handling of this situation.