are children someone has in another relationship and expenses factored into child support?

My husands ex is stating that her child is his and he received an order for paternity and child support. he currently is the main income of our home and three children. will his basic expenses such as rent, utilities, food, clothes be factored into that. if so what does he need to bring as prove when he goes to court? will the judge ask for any information on our children that he also has to take care of. I do work but only part time so he brings the main income into the home will the judge need to see my income as well? I obviously know he needs to pay if its his I just want to make sure our kids don't suffer as a result his income just covers our bills.