Yes, if he meets all the requirements to claim your child, he can. But since the one of the girls is not 'his' child, she will not qualify your fiancé for the child-related tax credits. The child has to be his adopted, fostered, or stepchild (related to) to qualify for the bigger credits. See the difference between qualifying dependents and qualifying children here. Other dependents qualify for the $500 tax credit, but not the Child Tax Credit.
Similar example from 12 Tricky Tax Dependent Dilemmas
Q. My girlfriend and her two-year-old son live with me and I basically pay all the expenses. Can I claim both of them as my dependents?
A. Yes, if they meet all the IRS requirements for dependents. Did they live with you all year long? Did you provide more than half of their support? Did both of them have gross income of less than $4,300 in 2020 or 2021? If you can answer YES to all three questions, then you may claim both your girlfriend and her son as your dependents. (This assumes your living arrangements don’t violate local law. See above.) Until recently, in this situation the boyfriend could not claim the child as a qualifying relative because the child was considered a qualifying child of the mother. However, the IRS now says if the parent’s income is so low that he or she doesn’t have to file a tax return, then the boyfriend who lives with the mother and child all year long can claim the mother and the child as OTHER dependents.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
