Have you ever felt this way too? What do you think is the best thing I would do?

I am a daughter of divorced parents they had divorce when were kids. When I was a kid I used to stay with my mom and because of being financially unable to send me to school I lived with my Aunt then the pandemic comes and here I am now in my Dad. Growing up and living through that different families I'm just so jealous that my mom and her new family bonds and my stepdad will do anything to buy what my half-siblings wanted and same goes with my dad and his new family. While us, me and my biological brother, whose stuck in between has nobody to lean on and nobody to ask for what we wanted. Everytime I'm gonna ask my Dad what I want he always says that He cannot do it but when his other child wants it he won't hesitate to buy it even if it's expensive. I've always wanted to move out but him and my stepmom wouldn't let me because nobody will take care of my half sister. If I'm gonna run away I don't have anyone to back me up so I don't have a choice but to stat. What would I do?