At some time, your parents received a child support order requiring dad to pay mom.   Find that order, and use it to file your own motion with the court for emancipation, and ask that the child support stop.  Sounds like mom is using the child support as ailimony instead of child support.  If you need assistance, of course an attorney would be more than willing to assist, or you can go to the court and ask the very friendly court staff how to file the motion.