My husband was married to a woman before me and they had a child together. When they first divorced, he was still in college, working part time and living with his parents, so his income, should the court have put into effect a child support order, would have fallen below the minimum needs standard. Since then, he has gone active duty military and we now have a child of our own. Now, the mother has remarried also and wishes to update a parenting plan, which is fine, but when we asked her if she wished to modify the child support, she said no, understanding that with an infant, we couldn't very well afford it, no matter what the court said. However, my husband's divorce attorney said that she can't waive child support, the state will make him pay even if she doesn't pursue it. The child is four years old and this hasn't happened yet, so how can they make him pay it if she doesn't want it?

Because the state has a legal obligation to work for the welfare of the child, also if the mother or child receives any welfare or support, the state will also come after him for repayment of part of that in many states.

Also he wants to pay, since she can wait 10 years and then sue for all back payments if she wanted to.

Also I am not sure what the min needs standard is, but even men with no job are required to pay a min amount that the states has set.

So while the mother of the child seems to be nice and helpful and most likely has offered not to try and collect child support so your husband will sign some agreement that she wants.

But yes, the state has a obligation to watch for the welfare of the child and if you go back into court, it is almost for sure the court will visit the child support issue if they see he is not paying.

Well, they are both military service members and she isn't collecting any kind of state aid for the child. She said she ONLY cares about the relationship my husband has with her, and she doesn't want to take any money from our family. I am a full time student with no income and our daughter is only a year old so we have to put her in daycare. We actually aren't going to court, we are amending the parenting plan without attorneys which is legal as long as the parties agree to the terms. And she can't make him back child support if there was no child support order in the first place. So until someone MAKES him pay, he's under no obligation. At least that's what the attorney said.

As long as she doesn't pursue child support through the court then you can make the arrangements out of court. At least the only way I have seen child support pursued is if the custodial parent applies for child support OR welfare.
As long as you can work out agreements without conflict then you shouldn't need to go to court. Keep documented records of all agreements and everything he spends on or gives to the mother and daughter.