Child Support

I am with a man that has a child from a previous relationship...he has been paying a weekly agreement to cover his sons daycare. He has been in school for 2 years now but my SO still sends the same amount. The baby mom now has 3 kids and recently sent papers for him to pay child support...is it a chance they could get him for more money. We have a child and she already gets about 25% of his check...He isn't a deadbeat along with sending money when we get him we buy him clothes, shoes, school supplies, and even his favorite snacks to take back to his mom's house with him. She sends us all his copays when he needs to go to the dr...they live in a different state and when she brings him we give her gas money as well. What more could she want as to why she is requesting child support?