Self reliance for an artistic child?

My younger cousin is autistic he is a 13 year old boy. His abilities to change are lacking in some areas in others he can cope, but since i can remember they have waited hand and foot since birth to today. Im afraid i will be his caregiver because his dads in the hospital weekly and his mom smokes three packs a day and that's an unexaggerated truth. The inevitable is i will have to care for him someday because they do not encourage independence my question is can i help him become independent and change his personality for the better when the day comes, or his extreme dependence set in stone.