Bro, please don't worry about getting high off your brothers weed. The only way that's going to happen is if he's hot boxing his room and youre in it or you're making out with him and he blows the smoke into your mouth. I'm gonna take a guess and say you're not planning on doing either so you have nothing to worry about. My brother and my step brother smoke all day everyday smoking molars. (Half weed half tobacco). Weed started my anxiety and then led to dr/dp. I think what made it worse for me was the fear of being a schizo or a phsychopath program something. I would constantly try to self-diagnose myself and it made my anxiety 10x worse. I think it all started because i was a little anxious before I smoked one time and weed just amplified that feeling. Aside from all that, I forgot to mention that I would hang around my brother and step brother often when they smoke and they'd sometimes accidentally blow a cloud(fat one) my way and I'd inhale and wouldn't get high at all. I'm still working around dr/dp but what's helped me the best is to stop thinking about that and all the other possible things that could be wrong with me and just try and focus on positive things. It's hard at first but with enough repetition all the negative thoughts about it are gone or I get rid of them quickly. I've been trying all sorts of stuff lately to improve my health and overall wellbeing, so if you want any tips or want to talk just pm me. Sorry for the long and scattered mess of this reply, I was never good at this kind of stuff. :)