The IRS is not basing the monthly child tax credit payments on 2018 returns. So the "grapevine" is incorrect unless exBF actually filed a 2019 or 2020 return and claimed your children.
If you have not yet done so-----you have to file a 2020 return that claims your children. You can use the recovery rebate credit on your 2020 return to get the 1st and/or 2nd stimulus payment if you did not receive them. The third stimulus is issued separately by the IRS. Did you receive any of those payments? Did you file a 2020 return that claimed your children? Was your 2020 return accepted? Has it been processed?
Here is is some information on how the monthly child tax credit payments work---read the links and the FAQ's thoroughly so you will see what you might need to do to get the payments. If you filed a 2020 return claiming your children it should be automatic for you, but there is a portal on the IRS site you can use if needed.
Stop worrying about what your exBF "might" do and file your own returns honestly and correctly; the IRS will sort it out and if exBF files fraudulently the IRS will sort it out and deal with him.
https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
https://www.irs.gov/newsroom/irs-announces-two-new-online-tools-to-help-families-manage-child-tax-cr...
IRS.gov/childtaxcredit2021,
https://www.irs.gov/credits-deductions/child-tax-credit-update-portal
https://www.kiplinger.com/taxes/602921/child-tax-credit-update-irs-sending-letters-to-families-who-m...
https://www.kiplinger.com/taxes/602431/child-tax-credit-2021-who-gets-3600-will-i-get-monthly-paymen...
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
