Guys I need help

I live in the same room with my brother and I've told him plenty of times since it's OUR room we can't just blast our phones in full volume and it gets annoying but he literally DOESN'T GET ITTT
I use headphones or put it on low volume but it gets so fucking frustrating and annoying when I have to remind him every 30 fucking minutes to lower his volume IUGHHHHHHHHH like is it SUCH a big deal to just keep it low enough for yourself to hear and not the whole building????????? Like I legit don't know how to stop this...even when I'm taking a nap it gets so irritating I hate it
Please give me a solution so that my brother will finally shut up and stop being annoying