I’m sure he could get in trouble and I was you I will would tu n him in for sure he needs to learn that it’s nit ok to do illegal things u deserve that money cause u have them
Should say on court documents who/how the children are claimed on taxes. If he didn’t follow it report him to the IRS!!!
If the kid are with you more then 5 months within the year you are to claim them but marriage can be different
If you’re still legally married and have no court papers that say he couldn’t do so, no, nothing you can do