The lineal relative by blood is the relative by blood of a person from whom that person is descended or he who is descended from that person.
The collateral relative by blood is the nonlineal relative of a person who is descended from the same common ancestor as that person himself is.

The degree of relationship by blood between a person and his lineal relative by blood shall be determined by counting the number of generations upwards or downwards from himself [as the case may be], one generation being taken as one degree. As between the person and his collateral relative, the degree of relationship shall be determined by the total number of generations counting upwards from himself to the common lineal ancestor and then from such common ancestor downwards to the relative by blood with whom the degree of relationship is to be determined.

The relative by marriage of a person includes the spouse of his relative by blood, the relative by blood of his spouse and the person who is married to the relative by blood of his spouse.

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.

Divorce terminates the relationship between relatives by marriage. The same rule is applicable to the annulment of marriage.