Encyclopedia of Canon Law (Legislative Theology)

Marriage Impediments and Causes of Nullity [2]

Canonical Laws [7]
Marriage Impediments and Causes of Nullity [2]

Can a son marry his father’s wife’s sister?
That is, if two sisters exist and the father marries the elder, can the son marry the younger sister? Is such a marriage lawful? We answer as follows:
Such a marriage is absolutely forbidden for the following reasons:
A. A son may not be his father’s brother-in-law in marriage.
B. The father’s wife is considered a mother to the son according to the Law; therefore, her sister is regarded as his aunt. And a man may not marry his aunt.
C. Such a marriage causes serious confusion in kinship and lineage.

Let us suppose, in this example of the son being his father’s brother-in-law, that the son bears a son, and the father bears a daughter. What would their relationship be? Would marriage between them be lawful?
From the mothers’ side, these two children would be first cousins, since each of their mothers is the sister of the other’s mother. As cousins, marriage could be permitted.
However, at the same time, the father’s daughter is also the son’s half-sister—his son’s aunt. She cannot marry him, for she is his aunt! That is, she would be both his aunt and his cousin!

How could reason, logic, and faith allow a marriage that produces such confused and contradictory kinship? Would the boy treat her as his aunt or as his cousin? With what feeling would he look at her, and by what relationship would he deal with her?

I was truly astonished when one of our sons asked me this question, as I thought it was self-evident and required no inquiry!

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Other Questions about Kinship

Some also ask about non-physical kinship, such as:
A. Is marriage allowed between those united by spiritual kinship through baptism? For example, can one marry a girl who was baptized with him in the same baptismal font when they were infants?
B. May one marry the daughter of his godparent, if that godparent was an unrelated man or woman and he is considered their spiritual child, and therefore a spiritual brother to their daughters?
C. Do all the previous kinship rules apply also to adopted sons, forbidding them from marrying those prohibited by familial kinship, as if the adoption were a natural, bodily relationship?

The article cannot contain all the answers, but I promise we shall return to this topic and respond to each question in due time.

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Concerning Marriage Impediments Also

It is not permitted to marry a wife’s sister, nor may a woman marry her husband’s brother.

We have received several questions about this topic:

1. Is this prohibition ecclesiastical or civil, issued by Emperor Justinian or Emperor Theodosius?

2. Was the royal intent behind this prohibition to prevent sisters from killing each other to marry a husband, or brothers from killing each other to marry a wife?

3. Can such marriage be permitted ecclesiastically, since the sister might best care for her sister’s children, or the brother best care for his brother’s children?

4. Did Christ Himself oppose a man taking his brother’s wife, when the Sadducees asked Him about the woman who had married seven brothers in succession after each died (Matthew 22)?

5. Was John the Baptist’s rebuke to Herod—“It is not lawful for you to have your brother’s wife” (Mark 6:18)—only because he took her while his brother was still alive?

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The Reasons

Marriage to a brother’s wife is forbidden by divine command.

This prohibition appears twice consecutively in the Book of Leviticus, where God commanded:
A. “If a man takes his brother’s wife, it is an unclean thing; he has uncovered his brother’s nakedness. They shall be childless” (Leviticus 20:21).
B. And again among the forbidden relationships: “You shall not uncover the nakedness of your brother’s wife; it is your brother’s nakedness” (Leviticus 18:16).

These sacred texts belong to the Law that the Lord gave to Moses for the people. We are bound by this clear and holy divine command.
How could such a marriage be allowed when the Lord Himself called it unclean?

The only exception, which no longer applies today, was given in Deuteronomy (Deut. 25:5–9), with three conditions:

1. A brother dies without a son.

2. His brother takes his wife to raise up offspring for the deceased brother—the firstborn son being legally counted as the child of the deceased.

3. The purpose is “so that his name may not be blotted out from Israel.”

If the deceased brother already had offspring, then it was forbidden for his brother to take his wife, according to Leviticus 20:21 and 18:16.

Therefore, marrying a brother’s widow to care for his children contradicts the teaching of Scripture, which permitted it only to raise offspring for a childless deceased brother.
Hence it was written: “The wife of the dead shall not be married outside the family to a stranger” (Deut. 25:5). St. John Chrysostom explained (in his commentary on Matthew 14) that no stranger is obliged to raise offspring for the deceased, but a brother might do so.

Today, however, no one can claim a child as belonging to his deceased brother, nor does the law permit it. The reason—“that his name not be blotted out from Israel”—is obsolete.

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Did Christ Permit It in the Sadducees’ Question?

The Sadducees’ question was not truly about marriage to a brother’s wife, but about the resurrection. They cited the old exception from Deuteronomy: a man dies childless, his brother marries the widow, then he dies without children, and so on through seven brothers. Then they asked mockingly: “In the resurrection, whose wife will she be? For they all had her” (Matthew 22:28).

They were not seeking a ruling on marriage, but trying to ridicule belief in the resurrection, which they denied.
Thus Luke records: “Then came to Him some of the Sadducees, who deny that there is any resurrection, and they asked Him” (Luke 20:27). Likewise, Mark says: “Then came to Him Sadducees, who say there is no resurrection, and they asked Him” (Mark 12:18).

Therefore, the Lord’s response dealt with the resurrection, not marriage law. He ignored their side example because they asked it only as a pretext.
As the Book of Acts explains: “For the Sadducees say that there is no resurrection, neither angel nor spirit” (Acts 23:8).

The story they cited fits the old Deuteronomic exception:

1. “The brother died having no children” (Matt. 22:24; Luke 20:28; Mark 12:19).

2. “His brother shall take his wife and raise up seed for his brother” (Mark 12:19; Matt. 22:24; Luke 20:28).

3. “Each of the seven died leaving no offspring” (Luke 20:31).

What does this have to do with our time? Who now marries his brother’s widow to raise up his brother’s name? Who now attributes his own son to his deceased brother?

Christ did not permit marriage to a brother’s wife in the New Testament, nor did He annul the Levitical prohibition (Leviticus 18:16; 20:21). He simply answered the Sadducees’ real question about resurrection.

As for John the Baptist’s rebuke to Herod—“It is not lawful for you to have your brother’s wife” (Mark 6:18)—we shall discuss its meaning in due course.

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