Did you have a lawyer for that lawsuit ?

It seems like this was a forsee-able situation....that if you won the lawsuit against your employer/WC, that you would also be successful in your SSDI claim. I can see why your ex would want the money from the lawsuit torwards child support, if your SSDI claim had taken years more, she shouldn't have to wait for the CS.

Your problem now is that the kids' backpay checks go to where the kids live. SSDI doesn't change their process because you have already paid. I think you have to go back to family court and address this issue quickly to arrange for your ex to reimburse you before the overpayment is considered a gift.