What if ex will not sign modification papers?

by Knapp
(Dallas, TX )

My husband has 4 children from a previous marriage in which he pays $1,100 per month. In August, their mother packed up and moved 2 1/2 hours away. The kids have been in our custody ever since. (Thankfully!)

My husband and the ex spoke in length about filing a modification to stop the child support order. The ex totally understood and agreed to the terms since she isn't nearby. My husband and I consulted and retained an attorney to file the Modification suit. The papers are totally done, but now the ex doesn't want to sign the papers. Literally nothing has changed in the custody papers except to halt the child support.

My question is what happens if the ex totally refuses to sign the papers? Can anything go through the courts without her or must she sign the papers?

(A little history: she (ex) never comes to get or see the kids. She always tells them she is coming but always backs out. Since August she has seen them for a total of 5 hours.)

Thank you for your help.
The Knapp Family