Article IX: Consanguinity

148. • I. Notion of consanguinity.

a) It is the propinquity of persons of whom one descends from another, or all descend from a proximate common stock through carnal generation.

b) Stock: the person from whom others descend.

Line: a series of persons of whom one descends from another, or who all descend from one stock.

Direct line: that which is constituted from persons of whom one descends from another.

Transverse or collateral line: that which is constituted from persons who have a common stock, without one descending from another.

Degree: the distance of one person from another in the same line.

Equal line: when collateral persons are distant from the common stock by an equal degree.

Unequal line: if collateral persons are distant from the common stock by a diverse degree.

c) Concerning the manner of computing degree.

1. In the direct line there are as many degrees as there are persons composing the line, the stock being removed. (Can. 96, § 2.)

Thus a grandson is consanguineous with his grandmother in the second degree.

2. In an equal collateral line there are as many degrees as there are persons in one tract of the line, the stock being removed. (ibid., § 3.)

Thus a brother and sister are in the first degree, first cousins in the second.

3. In an unequal collateral line there are as many degrees as there are persons in the tract of the line that belongs to him who is more distant from the common stock. (ibid.)

Thus a maternal uncle with his niece is consanguineous in the second degree.

149. • II. Extension of the impediment.

a) "§ 1. In the direct line of consanguinity matrimony is invalid between all ascendants and descendants, both legitimate and natural."

b) "§ 2. In the collateral line it is invalid up to the third degree inclusive."

c) "The impediment of matrimony is multiplied only as often as the common stock is multiplied." (Can. 1076.)

Multiplication of this kind of common stock can occur in three ways:

1. When the common ascendants already are consanguineous.

For example: Arnold has two sons, Lucius and Paul. Again Lucius begot Peter and Mary, and Paul begot John. John contracted matrimony with Mary and from her begot Angela. Peter begot Andrew. Between Andrew and Angela there is a twofold impediment of consanguinity, one in the second degree from the common stock Lucius, and the other in the third degree from the common stock Arnold.

                         ARNOLD
                            |
              -------------------------------
              |                             |
           LUCIUS                         PAUL
              |                             |
        -------------                       |
        |           |                       |
      PETER       MARY ---------------- JOHN
        |                                 |
      ANDREW                           ANGELA

2. When men who are consanguineous with each other have begotten offspring from women who are consanguineous with each other.

For example: Albert and Reginald, brothers, take in matrimony, the one Mary, the other Aloysia, sisters. From the former matrimony Louis is born, from the other Eugenia. Between Louis and Eugenia there exists a twofold impediment in the second degree of consanguinity, because they have a twofold common stock, namely the parents both of their father and of their mother.

3. When someone has offspring from consanguineous persons whom he successively married.

For example, Ambrose successively took Martha and Leopoldina, sisters, in matrimony. From the former he begot Benedict, from the other Augustine. Benedict begot Margaret and Augustine begot Leo. Between Leo and Margaret there is a twofold impediment of consanguinity, one in the second degree, the other in the third degree, because they have a twofold common stock, namely Ambrose, their grandfather, and Emmanuel, their great-grandfather.

                         EMMANUEL
                            |
              -------------------------------
              |                             |
           MARTHA                     LEOPOLDINA
              |                             |
              --------- AMBROSE ------------
              |                             |
          BENEDICT                     AUGUSTINE
              |                             |
          MARGARET                         LEO

d) An easy manner of detecting consanguinity.

On separate sheets, above the names of the betrothed persons, let the names of their ascendants be written up to the third degree. If names are found common to each betrothed person, the impediment is present. Otherwise it is not.

150. • III. The law in force before the Code.

Before the Code, i.e., before the day 19 May 1918:

a) the impediment in the collateral line extended up to the fourth degree inclusive.

b) The impediment was multiplied also when either one of the betrothed persons ascended to the common stock by multiple ways.

151. • IV. By what law consanguinity makes matrimony diriment.

a) In the direct line, most certainly by natural law in the first degree; and more probably also in any degree, even more remote.

b) In the collateral line, in the first degree, by natural law according to many, although others contradict.

In practice: "Let matrimony never be permitted, if any doubt lies beneath whether the parties are consanguineous in any degree of the direct line or in the first degree of the collateral line." (Can. 1076, § 3.)

c) In the collateral line beyond the first degree, no one doubts that the impediment is of merely ecclesiastical law.

152. • V. What concerning a brother and sister who, as unbelievers, contracted matrimony between themselves, if afterwards they are converted to the faith?

R. The Holy See should be consulted.

153. • VI. Dispensation.

a) In the third degree it is dispensed easily, less easily in the equal second degree, with difficulty in the second touching the first.

b) A dispensation is valid if in the petition or concession an error concerning the degree has crept in, provided that the degree really existing is inferior, or even though the multiplicity of the impediment in an equal or inferior degree has been passed over. (Can. 1052.)