(a) When either or both parents are legally responsible for a nonjoint child, a deduction for this obligation shall be calculated under this section if:
(1) the nonjoint child primarily resides in the parent's household; and
(2) the parent is not obligated to pay basic child support for the nonjoint child to the other parent or a legal custodian of the child under an existing child support order.
(b) The court shall use the guidelines under section 518A.35 to determine the basic child support obligation for the nonjoint child or children by using the gross income of the parent for whom the deduction is being calculated and the number of nonjoint children primarily residing in the parent's household. If the number of nonjoint children to be used for the determination is greater than two, the determination must be made using the number two instead of the greater number.
(c) The deduction for nonjoint children is 50 percent of the guideline amount determined under paragraph (b).