The relationship that a person has to the blood relatives of a spouse by virtue of the marriage.
The doctrine of affinity developed from a MAXIM of CANON LAW that a HUSBAND AND WIFE were made one by their marriage. There are three types of affinity. Direct affinity exists between the husband and his wife's relations by blood, or between the wife and the husband's relations by blood. Secondary affinity is between a spouse and the other spouse's relatives by marriage. Collateral affinity exists between a spouse and the relatives of the other spouse's relatives. The determination of affinity is important in various legal matters, such as deciding whether to prosecute a person for INCEST or whether to disqualify a juror for bias.