How can I get my parents support?

I am 19 years old and have a dream of becoming a professional basketball player. I've always wanted to be one as a kid, yet somewhat hid it from my parents. I have so much dedication to go along with my dream, but my whole family thinks becoming pro is unrealistic. I practice everyday, exercise, get up at 5a.m, run, and stay out late and shoot. My step dad told me I have to be home before 10p.m, so I cant stay out late and practice anymore. I live on this huge hill and without a car I find myself walking a mile up, and back down just to get back and forth. Than i have to walk to the nearest court from there. My long term goal is to go to the NBA, but my current goal is to make an ABA team. The ABA pays and its a few leagues lower than the NBA. My parents know how much work I put in to basketball and often make fun of me for playing so much. But my point is, how can I get them on my side? I really want this for myself, and if they're not going to support me than ill just use it as motivation.