My child is 20 years old now and my ex is asking for 50% coverage of medical bills. Am I still responsible?
It depends on your agreement or court order, which no one here has read. Call your lawyer. He will know.
Your ex had to have filed a motion relating to the request. What is the legal theory or factual background for the request? Was it in the original order? Is the child still in college?
Apparently, there is an outstanding child support order. Did you have an attorney during the initial legal matter? If not, you should seek legal consultation and representation for this current matter.