Can my ex-spouse reduce child support payments because he’s having another child with his new spouse?

Question: 
My ex-spouse and I signed a separation agreement that says our children will live with me and he will pay me $625 per month for child support. Now he says he's going to reduce his payments to $500 because he and his new spouse are having a baby. Can he just decide to do that?
Answer: 

No, he cannot reduce the payments unless you both agree or he goes to court and a judge sets a different amount. The judge will likely use the Child Support Guidelines. This means the amount will depend mainly on your ex-spouse's income and how many children the support is for. The fact that he is having another child with someone else is usually not, by itself, a reason for the judge to change the amount.