We've all done this as parents. Our kid does something wrong — maybe they hit their sibling — and we say to them, "Tell them you're sorry." They may not feel like saying it, but we make them do it anyway.
There is nothing wrong with that, as long as we are not too harsh in forcing the apology. We help them with the action in hopes their heart will follow.
But how do we explain true repentance to our kids? Here's an idea for you.
Repentance simply means to agree. When our child does something wrong, we want them to agree with us that they have done something wrong. If they agree and see why it is wrong, they will be less likely to do it again.
If your child won't say they are sorry, that means they don't agree that what they did is wrong. Maybe instead of forcing them to say sorry, it is time to ask your child why they don't agree that their action is wrong.
Repentance means agreement. Work toward getting agreement with your kids in times of conflict and then you will start to see more true repentance.