He's definitely obsessive over Arata but that's because he was someone he was truly in love with or cared deeply for. He's good-looking and does have his good points if you look closely in the manga. I think I forgive him in the end because he felt very guilty for his actions and is repenting (shown in the last chapter).
I think the doctor liked him (maybe, I'm not sure) because Ten was slightly messed up and the doctors job is to help people like that so I think he wanted to help... or something...
Sorry, if your brother truly care and love you in such a way like Ten, then I don't need it. I would rather be off alone.
Reread and still loved... Btu still don't understand the appeal of Ten though.... :-[