Sounds like he has behavioural issues. First off. Don't do that thing with the sandpaper. It scrapes off your epidermis and makes the area very painful to even the slightest touch. I was actually just like him when I was younger. I was always attacking my older brother and he wasn't allowed to fight back. But one day he snapped and came at me with 100% He smashed my nose, knocked the wind out of me, stomped me, And to finish he picked me up and body slammed me into a table. From that moment on I realized my violent outbursts could have dire consequences. Now I'm not telling you to beat up your brother. But maybe hit him back. Or better yet if you think you can. Pin him down. That way you humiliate him so he doesn't try it again. Establish that what he's doing wont fly with you. You're the older sibling and you have authority over him.