Article IV. Consanguinity

Consanguinity is the bond of relationship by blood existing between those who are descended by carnal generation from one and the same near stock. The relationship, therefore, arises from community of blood derived from a common and not too remote ancestor. That common ancestor is called the stock; the distance in descent between one person and the other is called the degree of relationship; and the series of persons who descend from the same stock is called the lie, which is direct if they descend from one another, otherwise it is collateral. The degrees are equal in the collateral line if the persons are equally distant from the common stock; otherwise they are unequal.

It is immaterial whether both parents of the common stock are the same or only one, and whether the birth be legitimate or not.

The method of computing the degrees differs somewhat in canon law from that adopted by modern English civil law, which here follows the Roman civil law. The following are the rules for reckoning the degree of relationship according to canon law, which is followed in moral theology:

(a) To find the degree of relationship in the direct line, count the persons, leaving out the common stock.

(b) In the collateral line, when the degrees are equal, count the persons in one of the lines of descent, leaving out the common stock.

(c) When the degrees are unequal, count the longer line, leaving out the common stock in the same way, and add the number of persons in the shorter line. Thus, an uncle and niece are related in the second degree, touching the first, or mixed with the first (Can. 96).

According to the English method of computation, which is also followed in most States of the Union, all the persons are counted both in the direct and collateral lines, leaving out the common stock. According to this method, an uncle and niece are in the third degree.

Consanguinity in the first degree of the direct line annuls marriage by the natural law; and in further degrees indefinitely, but more probably only by ecclesiastical law. In the collateral ‘ line it is disputed whether consanguinity in the first degree annuls marriage by the law of nature or not; it certainly does so to the third degree by ecclesiastical law.¹

This impediment, therefore, is partly of natural, partly of ecclesiastical law, and although in the more remote degrees of both the direct and collateral line it does not bind those who are not baptized, yet even among them there is a natural bond in blood relationship which after Baptism becomes a diriment impediment of marriage within the prohibited degrees. One who is baptized is subject to the laws of the Church, and cannot, without the necessary dispensation, marry a relation within the forbidden degrees, even if the latter is not baptized.

English law follows in this matter that of Leviticus, and according to its method of computation consanguinity is a diriment impediment of marriage to the third degree inclusive, but not beyond. Thus an uncle cannot marry a niece, but two cousins may marry, by English law.

¹ Council of Lat. 4 (1215); can. 1076.

The impediment of consanguinity may be multiple from various causes, but it is only multiplied as often as the common stock is multiplied (Can. 1076, sec. 2).

(a) If two near relations marry, their offspring will be related in several different ways: [diagram in the original]. In this scheme G and H are descended from the common stock C=F, and so they are in the second degree mixed with the first in the collateral line. Both G and H are also descended from A=B through C and through F. On this account they are in the third degree of relationship. Thus there is a double relationship between them, and if a dispensation were required for G to marry H, mention should be made of this fact.

(b) Similar results will follow if two relatives marry two relatives: [diagram in the original].

In this scheme G and H are descended from both A and B, and they are in double second degree of relationship.

(c) Similarly, if one man successively marries two who are related to each other: A D=B’ ‘C+D E F G H G and H are in the second degree from the common stock D, and in the third from the common to marry his deceased wife’s sister.

Affinity