The line and degree of relationship between relatives by marriage shall be determined as follows:
(1) In regard to the spouse of a relative by blood, by the line and degree of relationship of the person who is married to the said spouse;
(2) In regard to a relative by blood of a spouse, by the line and the degree of relationship between such relative by blood and the said spouse;
(3) In regard to the person who is married to the relative by blood of his spouse, by the line and the degree of relationship between such person and the said spouse.