Canon Law – Is It Permissible to Marry the Wife’s Sister or the Husband’s Brother?

First: The Theological Concept of Marriage

From a theological perspective, the two spouses become one in the sacrament of marriage. Accordingly:

• The wife’s relatives become relatives of the husband.

• The husband’s relatives become relatives of the wife.
  Thus, the wife’s sister is considered a sister to the husband, and the husband’s brother is considered a brother to the wife. Therefore, marrying either is theologically equivalent to marrying one’s own sibling and is completely rejected.

Second: The Permanence of Kinship

His Holiness Pope Shenouda III emphasizes that:

• The marital bond may end by death.

• But kinship does not end with death.
  Therefore, the death of the wife does not make her sister permissible to the husband, nor does the death of the husband make his brother permissible to the wife.

Third: Biblical Testimony

This prohibition has clear roots in the Old Testament, especially in Leviticus chapter 18, which lists forbidden marriages due to kinship. The New Testament also affirms this principle through the stance of John the Baptist against Herod’s marriage to his brother’s wife, declaring it unlawful.

Fourth: Apostolic Canons and Councils

His Holiness Pope Shenouda III reviews:

• Apostolic Canon 19, which considers such marriages invalid.

• The Canons of the Council of Neocaesarea (315 AD), prior to the Council of Nicaea, which imposed strict ecclesiastical penalties.

• The Canons of Saint Basil the Great, which explicitly prohibit these marriages and impose lengthy periods of repentance.

• The Canons of Saint Timothy of Alexandria, which even forbid clergy from participating in or blessing such marriages.

Fifth: Rejecting the Attribution to Justinian

His Holiness refutes the claim that this prohibition originates from Justinian’s laws, explaining that:

• Justinian merely adopted already established ecclesiastical laws.

• Church law preceded civil law by centuries.

Sixth: The Spiritual Purpose of the Prohibition

This prohibition serves to:

• Preserve chastity and purity within the family.

• Prevent temptation, suspicion, and relational disorder.

• Eliminate motives related to murder, greed, or personal gain.
  The absolute prohibition closes the door to evil at its roots.

Conclusion

Marriage to the wife’s sister or the husband’s brother is an unlawful and invalid marriage, rejected canonically, biblically, theologically, and traditionally. The Church has unanimously upheld this teaching from the Apostolic era through later centuries, safeguarding the sanctity of the sacrament of marriage, the purity of the family, and the peace of the ecclesial community.

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