Q. My ex-wife (common law) filed for child support under the Uniform Interstate Family Support act.

You'll need to file a suit to establish custody orders in whatever State the children have been living in for the last 6 months. If they haven't been living in the new State for 6 months yet, you may still be able to file in the State they moved from. Contact a lawyer to assist you with this, since interstate proceedings really are not do-it-yourself issues.