Do you plan to talk to him about the way you both are so similar? I think that's really interesting (for lack of a better word) and would be worth asking what he thinks about the way you both get along. I have felt a strong affinity with my therapist--we share some similar ideals and interests--but it's never crossed a boundary or made me wonder if we could be friends. There is a line there that's very solid and not at all concerning. From Kashi's reply to you, he sounds pretty secure in the framework you're working in, so I'd say that's a good sign.