I dislike my whole family

Hello, I’m a 15 year old female and I have been feeling like this for years since I was younger. Everyone in my family are either liars, narcissistic, self-centered, or just hard to be around in general. There is also another reason, whenever I was 11 my mom decided to have my younger brother who is autistic who just turned 4, my mom NEVER and I mean NEVER takes care of my brother. Me and my older sister who is 18 female is always changing his diaper (which idk why he is 4 in a diaper with grown men shit), I try to get him to drink more water and eat better because my mom lets my brother eat whatever the hell he wants so he always have cavities, we have to dress him, bathe him and my sister had bought him expensive shit that my mom should have bought, every single time we buy shit for my brother my mom never pays us back! People in my family fucking knows this and never says shit! They don’t care! So that is another reason why I despise my family. Thank you for hearing me out and any advice is very much appreciated.