being the sister of an autistic child. warning: harsh and not for everyone.

All my teenage years, my dream future was one where I wouldn't depend on anyone and no one would depend on me. One where I was completely free to do what I pleased whenever I pleased. It would be me, my job, my friends/bf/cat, and no one else forever. I never wanted kids because I have no interest in giving up my freedom to do whatever I wanted to have responsibility over an annoying kid that can't do anything without help. Why is this relevant? I have a brother who is on the autism spectrum and apparently my whole family has decided that it is my responsibility to take care of him when my parents can't, and it will be forever. My whole future will be built around whether my parents need me to play babysitter or not, and I have absolutely no choice in the matter because if I refuse to sacrifice my schedule for him/them, I am apparently being an irresponsible selfish bitch. My whole life I have been yearning to escape this situation at home where I have to watch my 14 year old brother behave like a 5 yr old, lose his neurotypical friends one by one because he is not normal, and be destined to a future where he depends on someone to take care of him because he has no clue how to survive on his own or of his surroundings. Apparently now I'll be tied to this situation for life, and I honestly can't take the thought. I am 17 fuckin years old, I shouldn't hate my own life so much. I can't bear the thought of being the only person my brother has in the world once my parents pass, of having the reminder of my shitty family situation living with me forever. What will happen if I die before him? What will happen if I forget about him once and something happens to him? My life is a mess wherever you look and I'm not even fully responsible for myself yet.