Introduction

In the Philippines, marriage is considered a sacred institution protected by the Constitution and governed primarily by the Family Code of the Philippines (Executive Order No. 209, as amended). The law emphasizes the permanence of marriage, with no absolute divorce available for Filipino citizens (except in cases involving Muslim Filipinos under the Code of Muslim Personal Laws or when one spouse is a foreigner under Article 26 of the Family Code). However, when a spouse engages in cohabitation with another partner—often indicative of infidelity—the aggrieved party has several legal remedies available. These remedies span criminal, civil, and family law actions, aimed at addressing emotional, financial, and familial consequences.

This article comprehensively explores all aspects of these remedies, including grounds, procedures, evidence requirements, potential outcomes, and related considerations. It is based on Philippine jurisprudence, statutes, and legal principles, but readers are advised to consult a licensed attorney for personalized advice, as outcomes depend on specific circumstances.

Grounds for Legal Action

When a spouse lives with another partner, this behavior typically falls under the umbrella of marital infidelity, which can trigger multiple legal grounds:

1. Sexual Infidelity as a Ground for Legal Separation

Under Article 55 of the Family Code, legal separation may be granted on grounds including:

Repeated physical violence or grossly abusive conduct.
Sexual infidelity or perversion.
Attempt on the life of the petitioner.
Abandonment without justifiable cause for more than one year.
Drug addiction, habitual alcoholism, or chronic gambling.

Cohabitation with another partner constitutes "sexual infidelity," which is sufficient cause for legal separation. Jurisprudence, such as in Dela Cruz v. Dela Cruz (G.R. No. 195650, 2012), interprets this broadly to include extramarital relationships that undermine the marital bond, even without direct proof of sexual acts if cohabitation is established.

2. Psychological Incapacity as a Ground for Nullity of Marriage

If the infidelity stems from a deeper psychological issue, it may support a petition for declaration of nullity under Article 36 of the Family Code. Psychological incapacity must be grave, juridically antecedent (existing at the time of marriage), and incurable, rendering the spouse incapable of fulfilling marital obligations. Cases like Republic v. Molina (G.R. No. 108763, 1997) outline criteria, including expert psychological evaluation. Cohabitation with another could evidence such incapacity if linked to personality disorders.

3. Bigamy or Concubinage/Adultery as Criminal Offenses

Adultery (Article 333, Revised Penal Code): Committed by a married woman who engages in sexual intercourse with a man not her husband, or by her paramour. Proof of cohabitation isn't required; a single act suffices, but living together strengthens the case.
Concubinage (Article 334, Revised Penal Code): Committed by a married man who keeps a mistress in the conjugal dwelling, has sexual intercourse under scandalous circumstances, or cohabits in any other place. Cohabitation is a key element here.
Bigamy (Article 349, Revised Penal Code): If the erring spouse attempts to marry the new partner without annulling the first marriage, this is a separate crime punishable by imprisonment.

These are public crimes, prosecutable by the state, but often initiated by the offended spouse's complaint.

4. Abandonment and Non-Support

If the spouse leaves the family home to live with another, this may constitute abandonment (Article 55, Family Code) or criminal non-support (Article 101, Family Code; Article 195, Revised Penal Code as amended by R.A. 9262). The aggrieved spouse can seek court-ordered support.

Procedures for Seeking Remedies

1. Filing for Legal Separation

Venue and Jurisdiction: Filed in the Family Court of the province or city where either spouse resides (Rule on Legal Separation, A.M. No. 02-11-11-SC).
Process:
- Petition must be verified and include allegations of grounds, with supporting affidavits.
- Service of summons on the respondent spouse.
- Pre-trial conference for possible reconciliation.
- Trial where evidence is presented (e.g., witness testimonies, photos, messages proving cohabitation).
- Decision: If granted, the court decrees separation, divides community property, and awards custody/support.
Cooling-Off Period: A mandatory six-month period from filing before trial to encourage reconciliation (Article 58, Family Code).
Effects: Spouses live separately, but marriage remains valid. Remarriage is prohibited. Property regime is dissolved, and the guilty spouse forfeits net profits from community property.

2. Petition for Annulment or Nullity

Grounds Specific to Infidelity: Annulment (Article 45) for fraud, force, or impotence; nullity (Article 36) for psychological incapacity.
Procedure (A.M. No. 02-11-10-SC):
- Filed in Family Court.
- Requires psychological report from an expert.
- Involves fiscal intervention to defend the marriage.
- Evidence must show incapacity existed at marriage, with cohabitation as manifestation.
Effects: If granted, marriage is void ab initio (from the beginning). Parties can remarry, property is divided, children remain legitimate.

3. Criminal Prosecution

Filing: Complaint-affidavit filed with the prosecutor's office (for preliminary investigation) or directly with the Municipal Trial Court for concubinage/adultery.
Evidence: Direct proof (e.g., eyewitnesses) or circumstantial (e.g., hotel records, joint residences, social media posts). The offended spouse must file within one year of discovery (prescription period).
Penalties:
- Adultery: Prision correccional (2 years 4 months to 6 years) for both parties.
- Concubinage: Prision correccional in minimum/medium (6 months to 4 years) for husband, destierro (banishment) for concubine.
Pardon: The offended spouse can pardon the offender before trial, extinguishing the case (Article 344, RPC).

4. Civil Actions for Damages

Under Articles 19-21 of the Civil Code, the aggrieved spouse can sue for moral damages due to abuse of rights or acts causing emotional suffering.
If involving violence or economic abuse, file under Republic Act No. 9262 (Anti-Violence Against Women and Their Children Act), which provides for protection orders, even if the victim is male.
Procedure: Filed as a separate civil case or integrated into family proceedings.

5. Custody, Support, and Property Issues

Child Custody: Tender years presumption favors the mother for children under 7 (Article 213, Family Code), but best interest of the child prevails. Infidelity may influence decisions if it affects parenting.
Support: Petition for support pendente lite (during proceedings) under Article 198, Family Code.
Property Division: In legal separation, absolute community or conjugal partnership is terminated (Articles 63, 134). Guilty spouse loses share in net profits.

Evidence Requirements

Proving cohabitation requires substantial evidence:

Testimonies from witnesses (e.g., neighbors, family).
Documentary proof: Lease agreements, utility bills in both names, bank statements showing shared expenses.
Digital evidence: Emails, texts, social media posts (admissible under Rules on Electronic Evidence, A.M. No. 01-7-01-SC).
Private investigators' reports, though courts scrutinize their credibility. Burden of proof is preponderance of evidence in civil cases, beyond reasonable doubt in criminal.

Defenses and Counterclaims

The erring spouse may defend by:

Denying facts or alleging condonation (forgiveness, Article 56, Family Code).
Counter-petition for separation on reciprocal grounds.
Claiming the relationship is platonic. Collusion (agreement to fabricate grounds) voids the petition (Article 48, Family Code).

Special Considerations

1. Impact on Children

Legitimacy is unaffected. Courts prioritize child welfare, potentially ordering counseling.

2. Same-Sex Relationships

Philippine law does not recognize same-sex marriage, but infidelity in heterosexual marriages applies similarly. R.A. 9262 protects against abuse in intimate relationships.

3. Overseas Filipinos

If one spouse is abroad, jurisdiction follows residence rules. Foreign judgments on divorce may be recognized if involving a foreigner (Article 26).

4. Costs and Duration

Proceedings can take 1-5 years, with costs including filing fees (P5,000-P20,000), attorney fees (P50,000+), and expert fees.

5. Alternative Dispute Resolution

Mediation is encouraged in family courts for amicable settlement.

6. Recent Developments

Jurisprudence evolves; e.g., Leonen v. Leonen (G.R. No. 221021, 2021) refined psychological incapacity standards, potentially easing nullity petitions linked to infidelity.

Conclusion

When a spouse lives with another partner, Philippine law provides robust remedies to protect the aggrieved party, though the process emphasizes reconciliation and family preservation. Legal separation offers immediate relief without dissolving the marriage, while nullity provides a path to freedom in severe cases. Criminal sanctions deter infidelity, and civil remedies address personal harms. Navigating these requires careful evidence gathering and professional legal assistance to ensure justice while minimizing emotional toll. Ultimately, these mechanisms uphold the sanctity of marriage while acknowledging human frailties.