I can't imagine anything that would be too personal for my T to ask me about. I'm there to talk about me, and my T isn't actually curious about me, he's just doing his job to help me improve my mental state. He's asked about my religion a couple of times, which was way more embarrassing than when he's asked about my sex life. But that doesn't mean it's inappropriate or wrong for him to ask - he's my T, so he has the right to ask. And I have the right not to answer - though we have a recent agreement, T and I, that he needs to push harder for answers.

I don't ask T questions about himself, unless it's to do with my therapy. I asked him how long he has until retirement, which I felt was a bit too personal, but he understood why I wanted to know. He always emphasises that nothing verbal is out of bounds, so I guess it wouldn't be inappropriate for me to ask him whether he is married or has children or whatever - it just feels very wrong to ask, so I don't.