(1) If an agreement is made in the same document in relation to 2 or more children, the document may be treated as if it contained separate agreements for each of the children.
(2) If:
(a) agreement is made in the same document in relation to a child or 2 or more children; and
(b) child support is to be payable to or by 2 or more parties to the agreement for the child or any of the children;
the document may be treated as if it contained separate agreements made in relation to the child or each of the children by each of the parties to or by whom child support is to be payable.