(a) When the obligation to support devolves upon two or more persons, the amount that each shall pay shall be proportioned to his respective estate. Nevertheless in cases of urgent necessity and under special circumstances, the judge may order one of them to provisionally provide such support, and he shall have the right to reclaim from the others their corresponding part of the amount.
(b) When two or more persons claim support at the same time of a person lawfully obliged to give it, and the latter has not sufficient means to attend to the needs of all, the order established in section 342 of this title shall be observed, except that support due to or on behalf of a child or children shall have priority over all other support obligations. Where there is more than one section 357 notice of withholding against a single obligor, preference must be given to payment of all current child support obligations before payment for any child support arrears and if the limits of section 303(b) of the Consumer Credit Protection Act (15 U.S.C. 1673(b)) preclude payment in full of all current child support obligations, then all of the current child support obligations shall be paid on a pro rata basis up to the limits of the Act.