SUBJECT: The Concept of ‘Incestuous Marriages’ and Public Policy

I. Introduction

This memorandum provides an exhaustive analysis of the concept of incestuous marriages under Philippine civil law and its intersection with public policy. The primary objective is to delineate the legal prohibitions, their underlying rationales rooted in public policy, and the consequential effects of such unions. The analysis will cover the specific prohibited degrees of relationship as enumerated in the Family Code of the Philippines, the absolute nullity of such marriages, and the relevant jurisprudential interpretations. A comparative analysis with select jurisdictions will also be presented to contextualize the Philippine legal stance.

II. Statement of Issues

What constitutes an incestuous marriage under the Family Code of the Philippines?

What is the foundational public policy rationale for prohibiting such marriages?

What are the legal consequences of an incestuous marriage, particularly regarding its validity and status?

How does Philippine law compare with other jurisdictions regarding prohibitions on consanguinity and affinity?

III. Applicable Laws and Doctrines

The Family Code of the Philippines (Executive Order No. 209, as amended):

Article 37: Defines incestuous marriages as those contracted between relatives within the prohibited degrees*.
Article 38: Enumerates the grounds for declaring a marriage void ab initio*, including those covered under Article 35.
Article 35(1): Specifically declares a marriage void from the beginning if contracted by parties below eighteen years of age, but more pertinently, its reference to other prohibited marriages* ties to Article 37.
* Article 37, in relation to Articles 38 and 35, is the central provision.

The Revised Penal Code (Act No. 3815, as amended):

Article 350: Defines and penalizes the crime of incest*.

Civil Code of the Philippines (Republic Act No. 386): The predecessor law on void marriages under its Article 80.

Relevant Jurisprudence: Supreme Court decisions interpreting these provisions.

IV. Legal Definition and Prohibited Degrees

An incestuous marriage is one contracted between parties who are related by blood (consanguinity) or by marriage (affinity) within the prohibited degrees as expressly defined by law. Article 37 of the Family Code states:
“Marriages between the following are incestuous and void from the beginning:
(1) Between ascendants and descendants of any degree; and
(2) Between brothers and sisters, whether of the full or half-blood.”
The prohibition based on affinity (relationship by marriage) is covered separately under Article 38(1), which declares a marriage void if contracted between parties who are related by affinity in the direct line or the collateral line within the fourth civil degree. However, the term “incestuous” in legal parlance is most strictly applied to the blood relationships in Article 37. The prohibition is absolute, admitting of no exception, and is not subject to dispensation by any authority.

V. Public Policy Rationale

The prohibition against incestuous marriages is considered a cornerstone of public policy for several interrelated reasons:

Morality and Public Order: Such unions are deemed contrary to universally accepted moral principles and the fundamental social order that the state seeks to protect. They violate the sanctity of the family structure.

Biological and Eugenic Concerns: A primary secular rationale is the prevention of genetic disorders and health defects in offspring resulting from the union of closely related individuals.

Protection of Family Integrity: The prohibition safeguards against the corruption of family relationships, where distinct roles of parent, child, and sibling must be preserved to prevent abuse, exploitation, and the distortion of familial authority and dynamics.

Psychological and Sociological Harm: It aims to prevent the psychological harm and social stigma that can afflict both the parties involved and any resulting children.

The law treats these considerations as so fundamental that the state has a compelling interest to nullify such marriages regardless of the consent or even the genuine affection of the parties.

VI. Legal Consequences and Imprescriptibility

An incestuous marriage under Article 37 is considered void ab initio (void from the beginning). It produces no legal effect whatsoever. The key consequences are:

Absolute Nullity: It is deemed never to have taken place in the eyes of the law. No marital bond is created.

No Need for a Judicial Declaration: While a judicial declaration of nullity is typically sought for clarity and to address collateral matters (e.g., property, use of surname), the marriage is ipso jure void. Any interested party may invoke its nullity at any time.

Imprescriptibility of Action: An action or defense for the declaration of its absolute nullity does not prescribe. It can be raised even decades after the ceremony.

Property Regime: The property relations of the parties are governed by the rules on co-ownership under the Civil Code, not by the absolute community or conjugal partnership of gains.

Parental Authority and Legitimacy: Children born from such a union are considered illegitimate children. However, they are entitled to support and successional rights as provided under Article 176 of the Family Code. Parental authority is governed by rules applicable to illegitimate children.

Criminal Liability: The parties may also be prosecuted for the crime of incest under Article 350 of the Revised Penal Code, which is a separate public offense.

VII. Comparative Analysis

The following table provides a comparative overview of prohibitions on consanguinity in selected jurisdictions. Note: This focuses on blood relationships; rules on affinity vary more widely.

Jurisdiction	Governing Law	Prohibited Degrees (Consanguinity)	Exceptions / Notes
Philippines	Family Code, Article 37	Ascendants & descendants (any degree); Siblings (full/half).	Absolute. No exceptions.
Japan	Civil Code, Article 734	Lineal relatives; Siblings; Aunt/Uncle & Nephew/Niece (3rd degree).	Marriage between adoptive parent and child prohibited but may be allowed after adoption is dissolved.
France	Civil Code, Articles 161-164	Lineal relatives; Siblings; Aunt/Uncle & Nephew/Niece.	The President may grant dispensations for compelling reasons in some collateral line cases.
Germany	Civil Code (BGB), § 1307	Lineal relatives; Siblings (full/half).	Marriage between adoptive relatives generally prohibited during adoption.
United States (Model)	Uniform Marriage and Divorce Act (Model)	Ascendants & descendants; Siblings (full/half); Aunt/Uncle & Nephew/Niece.	Varies significantly by state. Some states permit cousin marriages.
Singapore	Women’s Charter, Section 5	Ascendants & descendants; Siblings (includes adoptive).	Prohibition extends to adoptive relationships.
California, USA	Family Code § 2200	Ascendants & descendants; Siblings (full/half).	First cousins may marry under certain conditions (e.g., over 65, or one party sterile).

VIII. Relevant Jurisprudence

The Supreme Court has consistently upheld the absolute nature of the prohibition.
In Mercado v. Tan, (G.R. No. 137110, August 1, 2000), the Court emphasized that marriages between ascendants and descendants are incestuous and void ab initio for reasons of public policy. The Court stated that such a marriage is “so repugnant to our culture and is considered against the natural law.”
In Republic v. Court of Appeals and Molina (G.R. No. 108763, February 13, 1997), while primarily about psychological incapacity, the Court reiterated the imprescriptible nature of actions to declare a marriage void ab initio, which includes incestuous marriages.
In People v. Campuhan (G.R. No. 129433, March 30, 2000), the Court distinguished the crime of incest from an incestuous marriage, clarifying that the criminal act is the sexual intercourse itself between covered relatives, regardless of the existence of a marriage ceremony.

IX. Practical Implications and Procedure

For a person seeking to establish the nullity of an incestuous marriage, a petition for declaration of absolute nullity of marriage must be filed in Family Court. Despite the marriage being ipso jure void, a judicial declaration is necessary for:

Liquidating the co-ownership of property.

Addressing issues of child custody, support, and visitation.

Allowing either party to remarry legally, as the Certificate of Finality of the judgment serves as proof that no legal impediment exists.

Correcting the civil status in official records. The Solicitor General must be represented in such proceedings to ensure the protection of public policy.

X. Conclusion

The concept of incestuous marriages in Philippine law is defined with strict precision and is unequivocally declared void ab initio. The prohibition, encompassing ascendant-descendant and sibling relationships, is founded on immutable public policy considerations of morality, public health, and family integrity. The legal consequences are severe: no valid marriage exists, the action to declare nullity is imprescriptible, and criminal liability may attach. Comparative analysis shows the Philippine position to be among the most stringent, allowing no dispensation. Any union falling within Article 37 of the Family Code is a legal nullity, and the state maintains an unwavering interest in preventing and invalidating such relationships.