AFFINITY. - With this word, derived from the Latin affinitas (as if to signify, according to Modestinus [fr. 4, § 10, D. 38, 10], the drawing near of one generation ad fines alterius), is designated the juridical bond that binds one of the spouses to the blood relatives of the other.
The rules established on this matter by Roman law (among which the principal ones: affinitas non parit affinitatem; gradus affinitatis nulli sunt) were adopted without notable changes both by the civil legislations (see, for example, article 78 of the Italian Civil Code) and by the ecclesiastical one; which nevertheless preserved, until the promulgation of the Codex, the special characteristic of placing the foundation of affinity not only in marriage, but also in any illicit union between a man and a woman.
For the Latin canon law in force (can. 97) affinity derives from a valid marriage, whether merely rato, or rato and consummated. Whether it also derives from the marriage of two unbelievers and from that of a believer with an unbaptized person - that is, to use a more comprehensive term, from legitimate marriage (v. MATRIMONIO) - is disputed in doctrine. Although affinity has no lines and degrees of its own, it is calculated in such a way that in the line and degree in which someone is a blood relative of one of the spouses, he is an affine of the other spouse (for the definitions of direct and collateral line, as well as for the computation of degrees, v. CONSANGUINITÀ).
Besides constituting, within certain limits, a matrimonial impediment (of which will be said in the following §), affinity produces numerous juridical effects. Among them we recall: the incompatibility with the office of administrator of ecclesiastical goods, for anyone who is an affine in the first and second degree of the ordinarius loci (can. 1520, § 2); the prohibition of selling or leasing, without special license of the ordinary, the immovable goods of a church to anyone bound by affinity of the first or second degree to the administrators of the church itself (can. 1540); the obligation imposed on the judge, the promoter of justice and the defender of the bond to abstain from participating in those cases in which one of their affines has an interest (can. 1613, §§ 1-2); the incapacity to testify in judgment of those who are affines of one of the parties (can. 1757, § 3, n. 3), unless it is a matter of matrimonial questions (can. 1974) or of causes of beatification (can. 2027, § 1). Civil law, moreover, sanctions the reciprocal obligation of alimony (v.) between affines of the first degree in the direct line (It. Civ. Code, art. 433, nn. 4 and 5).
1. AFFINITY AS A MATRIMONIAL IMPEDIMENT
It goes back to the Mosaic legislation (Lev. 18, 8.14-18; 20, 11-12.14. 19-21; Deut. 27, 20.33), which severely forbade marriages with the stepmother, with the stepdaughter, with the daughter of the latter or of the stepson, with the mother-in-law, with the daughter-in-law, with the widow of the uncle and with the sister-in-law, excepted the case of levirate marriage (v. LEVIRATO, LEGGE DEL). Roman law recognized the impedimental efficacy of affinity limited to the first degree of the direct line; and to this disposition the Church conformed at first, which only at a later time was to extend the scope of the impediment up to the seventh degree of the collateral line and to institute, for the case of second and third marriages, a second and a third genus of affinity (v. TRIGENIA), afterwards suppressed by Innocent III at the Fourth Lateran Council (1215).
Today, in the Latin canon law, the impedimentum affinitatis is regulated by can. 1077 of the CIC, according to which affinity in the direct line dirimes marriage in any degree, while that in the collateral line renders it invalid up to the second degree included. It is a matter of an impediment of merely ecclesiastical origin, whose moral foundation must be traced both in those particular relations of familiarity and respect that usually arise between persons united by bonds of affinity, and in the expediency of extending as much as possible, by means of marriages between strangers, the mutual relations of charity and friendship of human families, and finally in the opportunity of removing the occasion and the danger of gravely sinful loves. It is by its nature perpetual and is multiplied: a) with the multiplication of the consanguinity from which it derives; b) with the successive passing to new marriages with a blood relative of the deceased spouse. From the impediment of affinity in the direct line the Holy See is not accustomed to dispense. It is easy, on the other hand, to obtain the dispensation when it is a matter of affinity in the collateral line, and especially in the second degree, which is a minor impediment.
Affinity constitutes a matrimonial impediment also for the civil legislations. According to art. 87 of the Italian Code, affines in the direct line and affines in the collateral line in the second degree (which corresponds to the first degree of the canonical computation) cannot contract marriage with each other.
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2. EASTERN CANON LAW
In Eastern canon law affinity subsists between each of those who have had sexual relations with each other, and the relatives of the other, whether this has occurred in marriage (affinitas ex copula licita) or outside it (affinitas ex copula illicita); it does not subsist, on the other hand, in the case of a non-consummated marriage.
The matrimonial impediment of affinity subsists in the direct line in any degree; in the collateral line ex copula licita, up to the eighth or seventh or sixth degree (included), according to the rite; in the collateral line ex copula illicita, up to the fourth degree included.
It is to be noted, however, that non-Catholic Easterners in general do not consider affinity ex copula illicita; and for that ex copula licita they recognize the matrimonial impediment at most up to the fourth degree.
Among the Easterners (with the exception of the Melkites) the degrees are calculated according to the civil computation (v. CONSANGUINITÀ).
For affinity of the second and third genus, in force among the Greeks limited to the matrimonial impediment, v. TRIGENIA.