Does your child say this?
When you’re raising or helping to raise a child that is not biologically your own, kids may sometimes use this fact against you during the heat of an argument.
When a child says “You’re not my mom or dad,” what they’re really trying to do is take the power away from you.
Focus on what your role is: caretaker. That means you should inform the child what the rules are in your house.
The whole idea here is to avoid a power struggle. What the child is doing is inviting you to a fight. And remember, you don’t have to attend every fight you’re invited to.
Avoid the power struggle, and calmly state what your role is and what the rules are.