What should I do about my little brother

So awhile back I got my Oculus quest and I've loved every second of useing it but, but one day my mom (I'm 15 pls spare me) told me to let my little brother (6 then 7 now) play I saw no problem at the time but it's gotten worse he's on it so much that if I tell him he can't get on he throw a fit and tells my mom, who always says he can get on, it's to the point that's basically his now. So far he has broke two of my controllers and the plastic ring around the lens but even after spending 100 dollars to replace both controllers that's still not enough to convince my mom to not let him play or at the very least set boundaries for him. My dad is the only one who understands that my headset that they bought FOR ME is mine and that I decided who can use it or not. I don't know what else to do, am I in the wrong or should I be more firm about how I feel. Thank you for any help