AFFINITAS AFFINITATIS. That connexion between two persons which has neither
consanguinity nor affinity; as, the connexion between the husband's brother
and the wife's sister. This connexion is formed not between the parties
themselves, nor between one of spouses and the kinsmen of the other, but
between the kinsmen of both. Ersk. Inst. B, 1, tit. 6, s. 8.