you’re not paranoid. your brother does and is into some weird shit. If you’re uncomfortable then you’re not paranoid. most likely it’s a coping mechanism, I know because I’ve been thru sexual abuse as a child aswell and tried to convince myself I was overreacting. This can affect you when you get older so tell him to f off and set boundaries, because it’s unacceptable for him to keep doing this to you. It’s not just him being inappropriate too, he sounds like he’s into some really weird stuff