13(4)If two persons claim the surviving spouse’s pension under this section, and one of those persons is a spouse because that person was married, other than in a void or voidable marriage, to the person referred to in subsection (1) at the time of that person’s death, that spouse is entitled to the surviving spouse’s pension, if otherwise eligible and subject to subsection 20.1(3), unless there is a valid written agreement between the person referred to in subsection (1) and that spouse, or a court order or judgment, that bars that spouse’s claim.