thumb|alt=refer to caption|A diagram in a Catholic children's [[catechism shows degrees of consanguinity and the impediments they pose to marriage.|343x343px]]
In Catholic canon law, affinity is an impediment to marriage of a couple due to the relationship which either party has as a result of a kinship relationship created by another marriage or as a result of extramarital intercourse. The relationships that give rise to the impediment have varied over time. Marriages and sexual relations between people in an affinity relationship are regarded as incest.
Today, the relevant principle within the Catholic Church is that "affinity does not beget affinity"—i.e., there is no affinity between one spouse's relatives and the other spouse's relatives. Canon 109 of the Code of Canon Law of the Catholic Church provides that affinity is an impediment to the marriage of a couple, and is a relationship which "arises from a valid marriage, even if not consummated, and exists between a man and the blood relatives of the woman and between the woman and the blood relatives of the man." Also, affinity "is reckoned in such a way that the blood relations of the man are related by affinity to the woman in the same line and the same degree, and vice versa."
Historical development
Mosaic law
In the Hebrew Bible, and contain prohibitions of sexual relations between a couple in a consanguineous relationship, as well as a number of prohibitions of certain affinity relationships, e.g., (father's wife), (father's brother's wife), (brother's wife), (wife's sister), (father's wife, daughter-in-law), (woman and her mother), (sister of either one's mother or father) and (brother's wife). Marriage to a brother's widow is prohibited, but not to a deceased wife's sister. However, as an exception, permitted a brother to marry his brother's widow if the brother died without issue, in a so-called levirate marriage. but had no degrees of affinity with regards to marriage. However, the rule was that, if an issue of affinity arose, at whatever consanguineal level a couple was joined was considered the same level as regarded affinity. Roman civil laws prohibited any marriage between parents and children, either in the ascending or descending line ad infinitum. Adoption was considered the same as affinity in that an adoptive father could not marry an unemancipated daughter or granddaughter even if the adoption had been dissolved. Slaves, as such, could not contract a legal marriage, but if freed were then subject to the general rules. Also, if contracted bona fide, out of ignorance of any impediment, a marriage that was contracted within the prohibited degrees of consanguinity or affinity was permitted to stand and any children thereof were considered legitimate.
Historical Catholic canon law
Regarding itself as not being bound by Old Testament commandments, the early Christian church followed Roman civil law, as the law of the land. The Christian emperors modified the rules from time to time and extended the civil law impediment to the first degree of collateral affinity. The church extended the impediment to relationships created by illicit intercourse. The Council of Elvira (), prohibited the marriage of a widower with his deceased wife's sister. The prohibition became slowly more extensive. By the early 9th century, the Western Church had increased the number of prohibited degrees of consanguinity from four to seven. The method of calculating relationships was also changed to simply count the number of generations back to a common ancestor. The church also prohibited affinity to the same seven degrees. While the impediment of affinity is close to but not as compelling as that of consanguinity, the reasoning behind the prohibited degrees of affinity being treated the same as that of consanguinity is the nearness to the blood relatives by the very act of sexual intercourse. The Council of Trent (1545–1563) limited the impediment to marriage on account of affinity in cases when the affinity is created outside of marriage (e.g., by force or extra-matrimonial intercourse) to the second degree of affinity. The Code of Canons of the Eastern Churches of the Eastern Catholic Church holds in Canon 809 that affinity invalidates marriage in the direct line in any degree, and also in the collateral line to the second degree, thus prohibiting someone from marrying their sibling-in-law without first receiving a dispensation.
The modern laws of the Anglican Church regarding affinity are found in the Book of Common Prayer, which were revised from time to time. The Deceased Wife's Sister's Marriage Act 1907 removed the impediment to marrying a late wife's sister. Restrictions were also relaxed by the Marriage Act 1949 s. 1 and the Marriage (Prohibited Degrees of Relationship) Act 1986 s. 1. The Anglican Communion allows marriages beyond the second degree of affinity.
The Eastern Orthodox Church relationship prohibitions because of affinity follow (father's wife), (father's brother's wife), (brother's wife), (wife's sister), (father's wife, daughter-in-law), (woman and her mother), (sister of either one's mother or father) and (brother's wife). However, the Greek patriarchs and bishops may grant dispensations with a certain degree of freedom or choose to adhere to the letter of the law. The Church of the East has few restrictions on affinity begetting affinity. The Armenian Apostolic Church restricts affinity to the fourth degree, while the policy of Oriental Orthodoxy in general is very close to that of the Roman Catholic canons.
See also
- Affinity (law)
- Consanguinity