My children mother to told me I am not the father of one of the kids I pay child support for both can I get a DNA test for one through the courts?

Over the past 3 years me and my kids mother has split up and I remarried every time she gets upset she claims the older child is not mine she put me on child support and I missed the first appointment due to the paperwork being sent to a relative's house that I used to live in and I did not have knowledge of my court date until after the date so I was not able to establish paternity at the first court hearing and I got put on child support w with no say-so of how much I can afford to pay and just recently because I wouldn't give her extra money on the side she stated again that I am not the older child's father what I be able to have the court order a paternity test for the older child?