My parent's are divorced, and in a stalemate. I'm out of the house, but they continue to fight over my little sister. My question is, can a parent come back years after both children are out of the house, claim that they were treated unfairly in the court ruling, and get more money in the form of child support?

Typically no, unless one parent can prove fraud. Something like one parent hiding assets. Have you browsed through the information in LawInfo's Free Legal Resource Center to learn more about your issue yet? See: http://www.lawinfo.com/consumer.html. You can certainly try to speak to a lawyer to determine what legal options may be available. In the meantime, you may be able to learn more on your own. Search the "Free Legal Resources" tab, or browse the Consumer Resources. Good luck.