I don't know what to do with my twin brother

my brother 18(m) complains about how our mom 48(f) yelles at him all the time and how i dont stand up for him. Our mom yelles at him for the exact same reasons, his room is always messy and he leave stuff out thats supposed to be in the fridge or he bites into fruit and leaves it on the counter, he also leaves our moms bathroom a mess and doesn't clean it up when he leaves mak8ng our mom clean it. also our mom tells him gently and doesn't shout to put things away but he never listens it's like he doenst care so our mom gets frustratedand starts yelling. I have tried communicating it with him telling him the reason our mom yells at him and how to fix it but he just blames me instead and tells me i dont protect him, but i dont protect him because i began noticing how all the arguments between him and our mom are about the same thing over and over Its been two days and he's called me slurs infron of our parents and even told me how he wanted to shoot me sometimes. I generally do not know what to do