In this situation the couple was divorced 2 months ago and they have 4 children total. The 2 oldest are in father's custody and the 2 youngest are in mother's custody. Mother is having problems with one of the youngest 2 children whom she has primary custody of. She is trying to force the child to live with his father (non-custodial parent). The divorce decree states very specifically that he is only to get the youngest 2 during the approved times and she is to get the oldest 2 during the approved times (which she doesn't do). Can she force the child to live with his father? (He is willing to have his son come live with him but wants it be "legal" before doing so. He paid for the initial divorce for both of them and now believes it should be her responsibility to pay for any changes since it was only finalized 2 months ago.) We're fearful she's going to keep changing her mind about where the child should live, claim parental kidnapping, etc. out of spite.

He's smart to want the custody order changed in the court...

Otherwise he will be paying to raise these kids but still be paying for HER to do it too... (as well as the other spite issues you mentioned)

Support paymnents would be modified to reflect the changes.

He's also got a valid point of if SHE wants the change now she should pick up the tab since he paid last time.