Whene my son father tried to claim his children

Yes someone has been claiming my children on there taxes for years. I noticed it win my kids dad triedto claim them n someone done it before he had the chance

Moved from here (https://www.askmehelpdesk.com/small-claims/someone-claimed-child-taxes-173519-3.html).

Notify the IRS that it appears that someone has been filing fraudulent returns.