I believe any contract they created was between the three “adults” involved. When the one adult who kept the child decided the citizens of the state needed to pay for the child’s upbringing, the state’s rules for providing assistance came into play.
The state’s citizens were never consulted when they made their original arrangement. If they truly wanted to keep their little private arrangement, the two mommies should be providing for the child not the citizens of the state.
Sounds about right to me...
Regards,
GtG