Now, in terms of your situation, I can't not to comment on your T insistence to break off contact with your brother. I understand from your description that your brother's behavior around underage girls may be more than just inappropriate. What I don't understand is why your T isn't just reporting it to the authorities if she believes that something is going on that deserves reporting? Why did she tell you that she'd have to report it IF you don't cut ties with him? What does reporting have to do with you having or not having a relationship with your brother?

She is a mandated reporter, as all therapists are. If she believes that your brother is sexually abusing minors, she is legally obligated to report it REGARDLESS of whether you have a relationship with your brother or not. Why is she making her reporting responsibility dependent on your continuous contact with your brother?