This is one for research. However, analogizing to social security disability payment for children's support, those are not considered for income purposes to the disabled parent and are considered property of the children. It would seem that the money you receive as and for child support should not be included as income for computing your support for the children of Mother 2, since that's what is used to support your children in part, despite that you have control over the funds and the payor spouse cannot make you account for the money. To get a determinative answer, you should have a consultation with a child support attorney.
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While the amount you receive as support is not included in your income for support purposes, I don't believe you can deduct the pro-rata share of child related expenses you pay for the children in your care. On the other hand, are these expenses "child support actually paid pursuant to court order or written agreement on behalf of any child for whom the parent has a legal duty of support and who is not subject to the instant action." It could fit that definition.
This is a very interesting question. I would love to know if any attorney has tried to make this argument in a prior case. If you are paying a substantial amount for these items and can prove the amount, it might be an argument worth making.
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