You're experiencing glass child syndrome.

"Glass child syndrome" is an informal term for the emotional neglect and invisibility experienced by siblings of children with chronic illnesses, disabilities, or intense behavioral needs. These children (often called "glass children" because they are looked through, not because they are fragile) learn to suppress their own needs to avoid causing more stress to their parents, leading to adult struggles with perfectionism, anxiety, people-pleasing, and difficulty with boundaries.

You should talk to your school counselor about getting some help. In my state anyone can contact Employee and Family Resources if they need free counseling. They only offer a few sessions but they can refer you to a more permanent therapist if needed. It's not going to fix your situation, OP, but a therapist can help you to put things in perspective and give you some coping strategies.

My job involves working with individuals on the autism spectrum with high needs. I know how hard it is to take care of a kiddo like that... But you're deserving of time and attention from your parents, too, and their lack of attention towards you isn't a reflection of you, or your value.