Affinity is a relationship of persons deriving from marriage. It arises from a valid marriage, whether consummated or not, and constitutes an impediment to sub-sequent marriages between a man and blood relations of his wife, and vice versa (Codex Iuris Canonicis cc. 109, 1092; Codex Canonum Ecclesiarium Orientalium cc. 919, 809). Affinity does not beget affinity; therefore, the blood relations of a man are not impeded by affinity from contracting marriage with the blood relations of his wife, nor are those of the woman with the blood relations of her husband.
In the direct line, the impediment of affinity extends indefinitely either ascending or descending. The impediment of affinity in the collateral line was abrogated in the Latin Church by the 1983 Code of Canon Law, but this impediment is retained in The Code of Canons of the Eastern Churches. Affinity in the second degree of the collateral line invalidates marriage in the Eastern Catholic churches (Codex Canonum Ecclesiarium Orientalium c. 809 §1).
History. Affinity was an impediment to marriage already in the Mosaic Law. A man was prohibited in the direct line from marrying his stepmother (Lv 18.8, 20.11; Dt 22.30, 27.20); his daughter-in-law (Lv 18.15, 20.12), his stepdaughter, stepson's daughter and stepdaughter's daughter (Lv 18.17), his mother-in-law (Lv 18.17, 20.14, Dt 27.23), and his stepsister (Lv 18.11); in the collateral line, his paternal uncle's wife (Lv 18.14, 20.20), his brother's wife (Lv 18.16, 20.21) except where the levirate law would apply, and the sister of his wife, the latter still living (Lv 18.18). Contrary to the last example, a man could marry two sisters simultaneously before the time of Moses; e.g., Jacob married Leah and Rachel simultaneously (Gn 29).
Although the above texts are addressed to the male, they are applicable reciprocally to the female also. Affinity in each case did not cease through death or divorce of the spouses who created it. The penalty for disregarding the impediment in the direct line was most frequently death (Lv 20.11, 12, 14). In the collateral line the penalty probably did not exceed the legal illegitimizing of offspring.
Carnal relations, licit or illicit, did not produce affinity. Nor was it marriage alone that created affinity but rather the contract of solemn engagement or sponsalia, which would be the equivalent of a ratified marriage. Reasons for declaring affinity an impediment might be cited as: (1) the respect and reserve that a person should naturally possess toward near relatives through blood or marriage, for marriage identified husband and wife in their unity of flesh (Gn 2.24); (2) the scandals that could arise from marriages between persons of close familial ties, in view of Oriental residence customs.
In the New Testament two instances reflect the application of affinity to marriage. The first was Herod Anti-pas's marriage with his brother's wife, Herodias (Mt 14.3, 4). The union was both adulterous, since Herod's brother was probably still living, and incestuous, as violating the Mosaic Law of affinity, which also obligated strangers living among the Jews (Lv 18.26). The second was the case of incest at Corinth mentioned in 1 Corinthians 5.1, in which a man was rebuked for marrying his stepmother, a crime punished by excommunication. Out-side of these two cases, nothing more about affinity appears in the New Testament.
Roman Law. The Roman law concerning affinity (adfinitas ) was founded upon valid marriage (justae nuptiae ) and related one consort to the kin of the other (Corpus iuris civilis, Digesta, ed. T. Mommsen and P. Krueger, 18.104.22.168, 8; Inst 1.10.6–10). Apparently affinity was considered an impediment only in the direct line reaching to infinity, but not in the collateral line (Dig 22.214.171.124). Prohibition of marriage was limited to affinity involving one's stepfather or stepmother and stepdaughter or stepson; and between father-in-law or mother-in-law and daughter-in-law or son-in-law (Dig 126.96.36.199–5), not descending one from another or from a common stock.
Conciliar Decrees. The Mosaic Law and Roman law were the sources used by the Church to formulate its own rules of affinity. For the first three centuries, the Mosaic Law was probably the only source. With decrees of Church councils such as those of Elvira (300–06) and Neo-Caesarea (314–25), and the Council of Rome (402), there were departures made from the Mosaic law, extending the impediment beyond the limits set by the Old Testament. Elvira forbade marriage with a stepdaughter and stepsister (c. 61, 66; J. D. Mansi, Sacorum Conciliorum nova et amplissima collectio 2.15, 16; C. J. von Hefele, Histoire des conciles d'après les documents originaux 1.256–57); Neo-Caesarea forbade marriage of a woman with her brother-in-law (c. 2; Sacorum Conciliorum nova et amplissima collectio 2.540; Histoire des conciles d'après les documents originaux 1.328). The Council of Rome forbade marriage with the deceased wife's sister and a deceased uncle's wife (c. 9, 11; Sacorum Conciliorum orum nova et amplissima collectio 3.1137; Histoire des conciles d'après les documents originaux 2.136–37). These decrees easily passed into the civil codes in the middle of the 4th century (Corpus iuris civilis, Codex Iustinianus, ed. P. Krueger, 188.8.131.52). Later councils extended the impediment still further to the widow of the paternal or maternal uncle, reaching as far as the seventh degree, and civil codes followed suit (e.g., Law of Visigoths 184.108.40.206 in Monumenta Germaniae Historica: Leges 1).
The ambit of affinity gradually evolved, particularly in the collateral line. From the 8th century the basis of affinity was changed from the marital contract (justae nuptiae ) to carnal intercourse (unitas carnis ). With corroboration from Scripture (Gn 2.24; 1 Cor 6.16), Saint Basil (379) had condemned marriage between a brother-in-law and sister-in-law (Letter 160, Patrologia Graeca, ed. J. P. Migne, 32:623). Saint Augustine mentioned the case later (Contra Faustum 1.22.61; Patrologia Latina, ed. J. P. Migne, 42:438; Corpus scriptorum ecclesiasticorum latinorum 25.1.656–57; Civ Corpus scriptorum ecclesiasticorum latinorum 40.2), and so did the author of a letter attributed by Saint Bede to Saint Gregory (Sacorum Conciliorum nova et amplissima collectio 10.407; Bede, Ecclesiastical History 1.27 in Patrologia Latina 95.60). The practical rule that resulted from this was that unitas carnis —carnal intercourse—made two persons one and established identity of relationship between oneself and relatives of a spouse, hence putting affinity on a plane with consanguinity. The Synod of Rome (721) then made this a juridic rule (Sacorum Conciliorum nova et amplissima collectio 12.263), and Gratian made it an adage of law (Corpus iuris canonici, ed. E. Friedberg, C.35 q.2, 3 c.15; C.35 q.5 c.3). The classical definition of affinity through Gratian became relationship of persons emanating from carnal intercourse.
By the 10th century the similarity between the impediments of affinity and those of consanguinity became complete. Roland Bandinellus (Pope Alexander III, 1159–81), a disciple of Gratian, concerning their mutual computation of degree stated: "The first type of affinity walks abreast [aequis passibus ambulat ] with consanguinity" (Corpus iuris canonici C.35 q.1). In the many vicissitudes during this period the two impediments reached as far as the seventh degree, although the actual force of the last two degrees fluctuated from one area to the next between diriment and impedient.
Since carnal relations (unitas carnis ) alone formed the basis of affinity, it was calculated identically with consanguinity. Most commentators became adherents of this principle with, however, some notable exceptions such as Saint Thomas, who maintained against the majority that it was marriage and not copula that formed the true basis of affinity (Summa theologiae Supplement 55.4.2). From the basis of unitas carnis, logic pushed the experts to develop their speculations about affinity unhindered. They distinguished four kinds of affinity. The first was that arising from marital (licit) or extramarital (illicit) sexual relations. Just when or where the concept of illicit affinity arose is unknown; however, some authors find the first trace in the Pseudo-Isidorian decretals of the 9th century. Once affinity was based upon sexual inter-course, the lack of ecclesiastical precepts respecting a public form of marriage created the difficulty of distinguishing between licit and illicit affinity.
The second kind of affinity arose between the man and the affines of the woman by the first type of affinity and vice versa. In this type a man could become related to the affines of a widow whom he married, and vice-versa. Extending this still further, the third kind of affinity would appear in a marriage between a man and the affines related to the woman by the second kind of affinity. These three main classes of affinity are illustrated by this example: Roger and Sylvia are married. The latter's first cousin, Catherine, is married to Julius. Catherine is associated with Roger by the first kind of affinity, Julius with Roger by the second kind of affinity, and following the death of Julius's wife and his remarriage, his new wife will be associated to Roger by the third type of affinity. The fourth type arose not from the sexual act but from generation and touched the offspring born of a second marriage, making them affines to the relatives of the first parent within the fourth degree (soboles ex secundis nuptiis ).
The principle of exogamy was not without benefit in the fusing of diverse peoples, but it caused inconveniences also in its subtle and complicated computations. The fourth Council of the Lateran (Sacorum Conciliorum nova et amplissima collectio 22.1028) in its 50th canon abolished all but the first kind of affinity and restricted its prohibitive power to the fourth degree in the collateral line arising from conjugal or extramarital carnal inter-course. The ancient rule had stated: affinity begets affinity. The new position stated the contrary: affinity does not beget affinity. The simple ancient definition of affinity, "relationship of persons proceeding from sexual inter-course" had to be augmented to read, "between a man and the blood relations of the woman, and vice versa." However valuable were these changes, illicit affinity remained to vex legalists. Also, legitimate affinity upheld to the fourth degree in the collateral line and to infinity in the direct line was still somewhat awkward to deal with.
The Council of Trent (1563) was unsatisfied with the work of the Lateran Council. In the collateral line it limited illicit affinity to the second degree. It upheld licit affinity to the fourth degree, as had the Lateran Council. It did not completely solve the difficulties of which it so vehemently complained in reforming the former law, and sub-sequent appeals from many bishops appeared in the Curia for relaxation of the impediment. Vatican Council I (1869–70) made no further changes.
It was left to the 1917 Code of Canon Law to make radical and far-reaching changes. Its most extreme modification was the change of the very basis of affinity from sexual intercourse to valid marriage entered into according to proper form. This represented a regression to the Roman civil law. As an impediment, it bound each spouse to the blood relations of the other. In the direct line the impediment extended to infinity but was limited in the collateral line to the second degree of affinity (1917 Codex Iuris Canonicis c.1077). The 1983 Code of Canon Law further refined church discipline regarding affinity.
Extent of Impediment. Because the marital impediment of affinity is a merely ecclesiastical law, it applies only to Catholics. Non-Catholic Christians and non-Christians are not considered bound by this impediment. However, the impediment would invalidate the marriage of a Catholic who has left the Church by a formal act.
Dispensation. Affinity is perpetual as an impediment and is not extinguished by passage of time or death of one of the parties. It is certain that it is an impediment of merely ecclesiastical law, therefore, the Church can and has dispensed from it. Dispensation from the impediment may be granted by a local ordinary or according to other provisions in Codex Iuris Canonicis cc. 1079–80 or Codex Coannonm Ecclesiarium Orientalium cc. 796–97.
Bibliography: p. dib, Dictionnaire de droit canonique, ed. r. naz, 7 v. (Paris 1935–65) 1:264–85.
af·fin·i·ty / əˈfinitē/ • n. (pl. -ties) (often affinity between/for/with) a spontaneous or natural liking or sympathy for someone or something: he has an affinity for the music of Berlioz. ∎ a similarity of characteristics suggesting a relationship, esp. a resemblance in structure between animals, plants, or languages: a building with no affinity to contemporary architectural styles. ∎ relationship, esp. by marriage as opposed to blood ties. ∎ chiefly Biochem. the degree to which a substance tends to combine with another: the affinity of hemoglobin for oxygen.
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.