I will be filing for my marriage to be annulled since my partner is still married with his 1st wife. I filed taxes for 2021 with his kids (my stepkids) and received the child tax credit for them he did not work. Will I have to pay that back? I gave him the money.
you may want to consult a tax lawyer. 2021 will probably need to be amended if you filed a joint or married filing separate return. you would have to file as single if you didn't have qualifying dependent(s) or possibly head of household if you did.
this would also apply to 2022, 2023 and 2024.
As Mike9241 mentioned, your filing status for that year will have to change to single, unless you also had children of your own that might qualify you for Head of Household. You need to amend the return, and file a single return and remove the children from your return.
One thing you might want to try is to claim innocent spouse relief, since you filed a return with your spouse and you didn't know he was also married to someone else at the time.
For more information refer to the following TurboTax and IRS links:
What is an innocent spouse and how does it differ from an injured spouse?
I am sorry that you are going through this.