I don't have kids, I'd tell them feel comfortable in your own room. Here's a door lock. When you're outside your room and hanging out we shouldn't see your junk. Maybe society shouldn't view nipples differently, but I'd also see telling your son to put in a shirt for breakfast
care to chime in a think piece of your own of why telling a 12 year old child that she shouldnt go braless around her OWN grandpa isn't?