Section 9. Consanguinity.

589. Nature of the Impediment. The impediment of consanguinity consists in this, that persons consanguineous in some certain degree cannot validly enter matrimony with each other.

a. Consanguinity is the nearness of persons descending by natural generation from the same proximate stock; therefore it arises from participation of the same blood. It is said proximate: for those who descend from a common remote stock (beyond the third generation) are no longer accustomed to be called consanguineous.

b. Consanguinity is legitimate if it arises from legitimate matrimony, and illegitimate if it arises from fornicary union; it is simple if it arises from only one source, and multiple if it arises from a double or multiple source.

c. It is clear that an impediment of matrimony arises equally from legitimate and from illegitimate consanguinity. Moreover, with regard to consanguinity which constitutes an impediment of matrimony, it makes no difference whether both parents or only one parent is common.

590. Declarations. In order that the impediment of consanguinity be rightly understood, three things must be explained: what stock is, what line is, what degree is.

1. Stock is said to be that person from whom others descend by natural generation, and in whom they come together as in a first root. Thus brothers have their father as stock; the children of two brothers have their grandfather as stock.

a. Ordinarily two persons, namely the parents, constitute the common stock; but it can also happen that one person constitutes it (whether man or woman), if this person had offspring not with one person but with several.

b. Because those born from the same stock share the same blood, they are called consanguineous. Consanguineous persons in the first degree of the collateral line are full or not full, according as they have both parents or only one parent in common. Those not full are called uterine if they have the same mother but a diverse father, and they are called consanguineous only if they have the same father but a diverse mother.

2. Line is the series of persons descending from the same stock through various generations. Line contains diverse degrees and is twofold, direct and oblique.

a. Direct line is the series of persons of whom one descends from the other, whether immediately, as a son from parents, or mediately, as a grandson from grandparents. Direct line is divided into two, one of which is of ascendants, from whom someone has origin, namely father, grandfather, great-grandfather, etc.; the other is of descendants, who have origin from someone, namely son, grandson, great-grandson, etc.

b. Oblique line (collateral, transverse) is the series of persons of whom one does not descend from the other, but nevertheless all have a common stock, as brothers, cousins.

The collateral line is either equal, if the persons placed in each line are distant from the common stock by the same degree, or unequal, if the persons placed in each line are distant from the common stock by a diverse degree. Thus two brothers are of an equal line, but a brother and a brother's daughter are of an unequal line.

3. Degree is the measure of the distance of one person from another in the same line. Degree can be simple or mixed.

591. Principles.¹ 1. In the direct line of consanguinity, matrimony is invalid between all ascendants and descendants, both legitimate and natural.

Therefore consanguinity dirimently impedes matrimony in any degree, by positive law at least, probably also by natural law.

Authors who affirm that consanguinity dirimently impedes matrimony indefinitely by natural law use this argument: all descendants owe to progenitors almost the same reverence which children owe to parents; therefore progenitors are accustomed to be called by the name parents, descendants by the name children. For this reason, consanguineous persons in the direct line are not judged to have received from God the power of handing over to each other the right over their bodies.

But those who affirm that consanguinity by the positive law now in force dirimently impedes matrimony indefinitely teach that the supreme pontiffs (Callistus I and Nicholas I in the responses to the consultation of the Bulgars) received into ecclesiastical law the dispositions of Roman law invalidating matrimony between consanguineous persons in any degree whatever.

2. In the collateral line, matrimony is invalid up to the third degree inclusively, but not beyond, even if a more remote degree is mixed with a nearer one, e.g., the fourth with the second.

The impediment, which formerly extended up to the seventh degree, was restricted by the Fourth Lateran Council under Innocent III, and afterward by the Council of Trent,² to the fourth degree, because of the great difficulty of observing the prohibitions of so many degrees, and by the new Code to the third degree. Therefore the fourth degree of consanguinity and the fourth touching the third no longer dirimently impede matrimony.

3. Matrimony is never to be permitted if a doubt remains whether the parties are consanguineous in some degree of the direct line or in the first degree of the collateral line, because the doubt is either certainly or probably of divine law.

¹ Cn. 1076.

² Sess. 24, c. 4, De reform. matr.

592. Origin of the Impediment. 1. In the first degree of the direct line (between father and daughter, mother and son) the impediment is certainly of natural law; in other degrees of the direct line marriages likewise seem to be invalid by natural law (secondarily), although some authors say that they are valid but illicit.

The reason of the first: by the natural light of reason itself we understand that the use of matrimony between consanguineous persons in the first degree of the direct line is contrary to the singular reverence owed to parents. Therefore almost all peoples not depraved in morals detest nuptials in the first degree of the direct line as wicked.¹ Wherefore, because of the natural baseness which inheres in marriages of this sort, consanguineous persons in the first degree of the direct line are judged by natural law to lack the power of handing over to each other the right over their bodies.

The reason of the second: all descendants indeed owe reverence to their progenitors, yet in a more remote degree this need not be so great as in the first. Wherefore nuptials between consanguineous persons also of a more remote degree of the direct line are opposed to natural law; but this repugnance does not seem to be so great that nuptials of this sort must be said to be absolutely invalid by natural law, but only by secondary natural law.

2. In the first degree of the collateral line (between brother and sister) the impediment is of natural law;² in the other degrees of the collateral line it is certainly of merely ecclesiastical law.

a. Several authors, both ancient and recent, deny that matrimony between brother and sister is invalid by natural law. And rightly indeed, if this is understood of primary natural law: for that singular reverence owed to parents, because of which nature itself forbids matrimony between parents and children, is founded chiefly in this, that parents are the principle of children. But in the collateral line this chief reason does not have force. Therefore nature does not absolutely forbid matrimony between brothers and sisters as it does between parents and children.³ Wherefore at the beginning, because of the most grave necessity of propagating the human race, which God willed to descend from one man, marriages between the sons and daughters of Adam were valid by divine disposition; but afterward, when the human race had already been sufficiently propagated, they became invalid by natural law.

b. Therefore concerning marriages which consanguineous infidels enter within the degrees prohibited by the Church, these things must be held:

a. Marriages entered between consanguineous persons in the first degree of the direct line are certainly invalid. The same must be said of marriages of consanguineous persons which are invalidated by civil law.

b. Matrimony entered between grandfather and granddaughter, and matrimony entered between brother and sister, is likewise invalid. If spouses of this sort are converted to the faith, they can enter a new matrimony according to the practice observed by the Holy See. If doubt remains concerning the value of a matrimony contracted in infidelity, one must stand for the nullity of the matrimony in favor of the faith.⁴

c. Marriages of consanguineous persons in the second and further degree, if nothing else stands in the way, are valid; and if the spouses are converted to the faith, they can remain in the contracted matrimony without dispensation.

3. The reason for prohibiting marriages to be contracted between consanguineous persons is chiefly threefold: one social, that mutual charity and friendship may be extended more widely; another moral, that, once hope of matrimony has been taken away, carnal love among members of the family may be restrained; and finally another physical, that provision may be made for offspring. For it is established that marriages of consanguineous persons are either unfruitful or that offspring often suffer from diseases and defects.⁵

¹ The Assyrians and Persians are to be excepted, who did not reject marriages between a son and his own mother; the Egyptians permitted marriages between brother and sister.

² Council of Trent, sess. 24, c. 5, De reform. matr.

³ Gen. 20, 12.

⁴ S. Office, May 18, 1872.

⁵ Cf. Wernz IV, n. 413 ff.

593. Canonical Computation of Degrees.¹ For computing degrees of consanguinity in canon law, three rules are established: one for the direct line, another for the equal collateral line, another for the unequal collateral line.

1. In the direct line there are numbered as many degrees as there are persons, the stock being removed, or there are as many degrees as there are generations.

Descendants          Titius.          Ascendants

1                                      1
Son                                    Father

2                                      2
Grandson                               Grandfather

3                                      3
Great-grandson                         Great-grandfather

Therefore father and son are consanguineous in the first degree, grandfather and grandson in the second, great-grandfather and great-grandson in the third.

In the appended schema Titius is consanguineous in the direct line with his father and son in the first degree, with his grandfather and grandson in the second, and with his great-grandfather and great-grandson in the third.

2. In the equal collateral line there are numbered as many degrees as there are persons on one side, the stock being removed. Therefore two persons are consanguineous in that degree by which they are distant from the common stock.

                 Claudius.

1                         1
       Anna                     Titius

2                         2
     Iacobus                   Theresia

3                         3
      Maria                    Iulius

Therefore brother and sister are consanguineous in the first degree of the equal collateral line; the children of a brother and the children of a sister (paternal and maternal cousins) in the second; the grandchildren of a brother and the grandchildren of a sister in the third.

In the appended schema, Iulius and Maria are consanguineous in the third degree, Iacobus and Theresia in the second, Titius and Anna in the first degree of the equal collateral line.

3. In the unequal collateral line there are numbered as many degrees as there are persons on the more remote side, the stock being removed. Therefore two persons are consanguineous in that degree by which the more remote person is distant from the common stock.

                 Sempronius.

1                         1
      Flavia                    Lucius

2                         2
       Anna                     Petrus

3                         3
      Caesar                    Victor

4
                                Melania

If therefore on one side there are three persons, and on the other side four persons, the stock being removed, the last two persons are consanguineous in the fourth degree of the unequal collateral line. A mixed degree of this sort is customarily expressed in this way: A and B are consanguineous in the fourth degree mixed with the third, or also in the fourth degree touching the third.

In the appended schema Melania and Caesar are consanguineous in the fourth degree touching the third. Victor and Anna are in the third degree touching the second, Petrus and Flavia in the second degree touching the first of the unequal collateral line.

¹ Cn. 96.

594. Names of Consanguineous Persons. 1. Names of ascending consanguineous persons in the direct line on the part of the father and mother:

First degree: pater, Vater; mater, Mutter.

Second degree: avus, Grossvater; avia, Grossmutter.

Third degree: proavus, Urgrossvater; proavia, Urgrossmutter.

2. Names of descending consanguineous persons in the direct line on the part of the father and mother:

First degree: filius, Sohn; filia, Tochter.

Second degree: nepos, Enkel; neptis, Enkelin.

Third degree: pronepos, Urenkel; proneptis, Urenkelin.

3. Names of descending consanguineous persons in the collateral line on the part of the father:

First degree: frater, Bruder; soror, Schwester.

Second degree: patrueles, Geschwisterkinder, when the two fathers are brothers; amitini, Geschwisterkinder, when the father of one and the mother of the other are siblings.

Third degree: patrueles magni, amitini magni, other Geschwisterkinder.

4. Series of descending consanguineous persons in the collateral line on the part of the mother:

First degree: frater, Bruder; soror, Schwester.

Second degree: consobrini, Geschwisterkinder whose mothers are sisters.

Third degree: consobrini magni, other Geschwisterkinder.

5. Names of ascending consanguineous persons in the collateral line on the part of the father:

First degree: patruus, Onkel (father's brother); amita, Tante (father's sister).

Second degree: patruus magnus, Grossonkel (grandfather's brother); amita magna, Grosstante (grandfather's sister).

Third degree: propatruus, great-grandfather's brother; proamita, great-grandfather's sister.

6. Names of ascending consanguineous persons in the collateral line on the part of the mother:

First degree: avunculus, Oheim (mother's brother); matertera, Muhme (mother's sister).

Second degree: avunculus magnus, Grossoheim (grandmother's brother); matertera magna, Grossmuhme (grandmother's sister).

Third degree: proavunculus, great-grandmother's brother; promatertera, great-grandmother's sister.

595. On Multiple Consanguinity. From multiple consanguinity there arises a multiple impediment of consanguinity. Now consanguinity is multiple if two persons come together in several stocks.¹

        Aloisius              Stanislaus

Caius        Leo - Agnes        Bertha

Cornelius       Petrus  Anna       Maria

Cornelius, the betrothed man, and Anna, the betrothed woman, descend from a double stock (Aloisius and Stanislaus). Therefore they are consanguineous in the second equal degree both from the stock Aloisius and from the stock Stanislaus.

Double Diverse Stock.

                         Carolus

Petrus          Maria          Anna

Iacobus          Henricus

Felix           Lucia

Felix, the betrothed man, and Lucia, the betrothed woman, descend from a double stock (Petrus and Carolus). Therefore they are consanguineous in the second equal degree from the stock Petrus and in the third equal degree from the stock Carolus.

Two Causes in One and the Same Marriage.

                         Iulius

Pius                      Leo

Caia      Flavia   Titus        Paulus

Linus                 Anna

Linus, the betrothed man, and Anna, the betrothed woman, are consanguineous in a double second degree, because they descend from a double stock (Pius and Leo); moreover, in the third degree, because they descend from the common stock Iulius.

¹ Cn. 1076, 2: "The impediment is multiplied only as many times as the common stock is multiplied"; formerly it was multiplied also when two persons descended from the same stock by a multiple way.

596. Note 1. In order to detect whether, and what kind of, impediment of consanguinity exists between two betrothed persons, the more apt method, namely where the stock is unknown, seems to be this: that above the names of the betrothed man and woman there be written the names of father and mother, grandfather and grandmother, and so on up to the fourth generation. If among the ascendants of each, thus described, no common stock is found, no kinship intervenes between them; but if among the ascendants a common stock is found, the degree by which each is distant from it must be computed. Once this has been done, it will be established what kind of consanguinity exists between them.

Note 2. From what has been said it is clear that between the law hitherto in force and the new Code there is a twofold difference with regard to the impediment of consanguinity:

a. Hitherto consanguinity dirimently impeded matrimony in the direct line indefinitely in any degree whatever, in the collateral line up to the fourth degree; now it dirimently impedes matrimony in the direct line indefinitely, in the collateral line up to the third degree inclusively. Therefore consanguinity in the fourth degree and in the fourth degree touching the third no longer dirimently impedes matrimony.

b. Hitherto the impediment was multiplied both from plurality of stocks and from plurality of ways through which one could ascend to the stock; now it is multiplied from plurality of stocks only.