Hal_Al
Level 15

Get your taxes done using TurboTax

You file an amended 2015 return claiming the kids. That will send the IRS after the boyfriend to make him pay back what he got. They will send you an additional refund based on your claiming the kids. At some point you may have to prove the kids lived with you.
Filing a return (in you case an amended return) will accomplish both of your purposes: 1. report him &  2. Get you that money