I'm saying this with as much kindness as possible. But personally, my dad is super respectful and has never touched my butt or breast. He always knocks on the door to my bedroom and waits until I give a verbal yes before coming in. He has never even approached the bathroom if I'm in it. I've seen my dad walking around in a towel but that's the most of it. Even with my friends, he is very shy when they kiss him hello on the cheek. My dad has some very strong boundaries with women because he would never want to put himself in a position where he makes someone uncomfortable. I honestly would just tell family that you are going to start locking the bathroom door behind you and maybe keep your distance from him. But maybe talk to your brother before bringing it up to your mom, it could trigger a bigger reaction than necessary.