69. Persons who are spouses within the meaning of section 19 at any time during a year are considered spouses for the year. Where an adult has more than one spouse in a year,(1) the adult is deemed to have only one spouse in the year;
(2) the person who is the adult’s spouse on the last day of the year or, if the adult has no spouse on the last day of the year, the last person to have been the adult’s spouse in the year is deemed to be the adult’s spouse for the year; and
(3) the adult is deemed not to be the spouse of any person other than the person referred to in subparagraph 2 in the year.
An adult is a person other than a dependent child.