No! I had the same problem with my e husband. Contact the IRS (I believe you have to contact them in writing about this. Its been yrs but I believe thats what I had to do) Explain to them what happend. That she claimed YOUR kids and they allowed her to with NO PROOF she had the right to do so. They will then launch an investigation and she will be set straight. Ofcourse this takes time. And I also contacted our divorce attorney. You can take her to court and make HER PAY the expenses because it was her that broke the law. (the attorney thing will be faster than dealing with the IRS) But I reccommend you get them both on board to what she did.