Do you like knowing your brother definitely came to the thought of his own sister right after he spied on you? I think its perfectly natural to be sexually curious about family because you're already around them so much. Which makes it way more likely for a brother to get a chance to spy on his sister or mother when he's curious to see a real woman. I would watch my mom get changed almost every day growing up and there's no way she didn't know I was watching but would still leave her door open because I think she thought is was just natural to have curious sexual thoughts about family. I think you should let your brother watch you like my mom let me watch her because its nice to have your first sexual fascination be with someone you already care about. Growing up with a mom who was comfortable with me exploring her body and getting off to her was way more healthy than watching porn at a young age. It felt nice knowing I was cumming for my mom who cared about me and you should consider doing the same for your brother. The relationship for me let me get so comfortable that my mom would even be ok with watching me masturbate to her because she knew I wanted to show her. I still love having my mom catch me touching myself and having her stay and encourage me to cum just for her. It seems like you want to be caught too so you should explore how close you can get to your brother since he's obviously interested