In regards to the “parents at fault” issue. Sometimes that is true. But often you can have a family with five kids, and four of them are terrific, ehrliche frum kids, but sadly one goes off the derech. So who brought up that fifth kid? You can’t blame parents all the time. The reverse is also true, parents can be the worst, yet one or more of their kids turn out to be exceptional, in spite of their terrible upbringing. Do those parents deserve the credit??? People are responsible for their own actions. we make choices, and some of them are not good ones.
I think the parents’ rov should be approached and asked for advice how to handle this. It might be better coming from him, as opposed to you.