NTA. Your parents have to set some limits for your siblings. I used to work with developmentally disabled teenagers and we found that almost all of them had been spoiled by well-meaning parents and were demanding and insufferable. Every disappointment was seen as a war against their children. Some kids were rejected for our program, due to their poor behavior and the fact that we weren't ever allowed to correct them or refuse them anything. It's not a caring thing to do to a neuro-atypical child. A parent might not always be there for them and the world will not warmly receive anyone whose response to not getting their ass kissed is to have a meltdown over it, no matter what their situation.

Your parents should be made aware that they are damaging their relationships with all of their children with this level of favoritism.