Wis. Stat. § 851.30: Surviving spouse.

(1) Subject to sub. (2), “surviving spouse” means a person who was married to the decedent at the time of the decedent’s death.

(2) “Surviving spouse” does not include any of the following:

(a) An individual who obtains or consents to a final decree or judgment of divorce from the decedent or an annulment of their marriage, if the decree or judgment is not recognized as valid in this state, unless they subsequently participate in a marriage ceremony purporting to marry each other or they subsequently hold themselves out as husband and wife.

(b) An individual who, following an invalid decree or judgment of divorce or annulment obtained by the decedent, participates in a marriage ceremony with a 3rd individual.

(c) An individual who was party to a valid proceeding concluded by an order purporting to terminate all property rights based on the marriage.