The father of one's son- or daughter-in-law; that is, the father-in-law of one's child, or, the father of one spouse in relation to the father of the other spouse; either of two or more men whose children marry each other, such as the father of a bride vis-à-vis the father of the groom.
Co-relative-in-law: A relative of one's generation, separated by two degrees of marriage.
A relative of one's generation, separated by one degree of marriage.