Non court ordered child support aggreement

Good day,
My husband has 5 children and two on the way. Twototal will be with me and twins on the way. As of now, he pays $1300 in child suppport of the three that are not mine. Two of the children are from divorced marriages so the payment is documented in the divorce decree. However, the third child was an agreement made between my husband and the child's mother that was notarized. The child was born overseas so there is no state jurisdiction over her. She is an american b/c her mom is military. Since finding out we will be having two additional children he elected to lower the agreed upon amount with the mother that there is no court order for. She said that she is going to take us to court, so I would like to know what can we expect. After the twins arrive, my husband will have a total of 7 children, will this be taken into account when calculating the amount of support to be paid? We want to be fair, but we want to be able to support our 4 as well.
Thank you!!