In the Philippines, the legal landscape surrounding marital infidelity is deeply rooted in the Revised Penal Code and special laws like Republic Act No. 9262. When a husband engages in an affair or moves in with a partner, the legal remedies available to the wife are specific, nuanced, and carry different evidentiary requirements.

1. Concubinage vs. Adultery

A common misconception is that "adultery" applies to both genders. In Philippine law, these are two distinct crimes with different elements and penalties.

Adultery (Article 333, RPC)

This is committed by a married woman who has sexual intercourse with a man not her husband, and by the man who has carnal knowledge of her knowing she is married.

Proof required: A single act of sexual intercourse is sufficient.

Concubinage (Article 334, RPC)

This is the crime applicable to a married husband. It is generally considered harder to prove than adultery because it requires more than just a single act of infidelity. To convict a husband of concubinage, one of the following must be proven:

He keeps a mistress in the conjugal dwelling (the family home).
He has sexual intercourse under scandalous circumstances.
He cohabits (lives together) with his mistress in any other place.

Note on Penalties: The penalty for concubinage is significantly lower than that for adultery. A guilty husband faces prision correccional (short-term imprisonment), while the mistress is only given the penalty of destierro (banishment from a specific radius).

2. R.A. 9262: The VAWC Law

Because concubinage is difficult to prove, many aggrieved wives turn to Republic Act No. 9262, or the Anti-Violence Against Women and Their Children Act of 2004.

The law recognizes that an affair is not just a breach of marital vows, but a form of Psychological Violence.

Psychological and Emotional Anguish

Under Section 5(i) of RA 9262, causing mental or emotional anguish to a wife—which includes maintaining an affair or a "second family"—is a criminal offense.

Advantage: Unlike concubinage, you do not necessarily need to prove the "scandalous" nature of the affair or the "cohabitation." The focus is on the suffering and emotional trauma inflicted on the wife.
Remedy: The wife can file for a Protection Order (BPO, TPO, or PPO) to remove the husband from the home and prevent further harassment.

3. Civil Remedies and Support

Beyond criminal prosecution, the wife has several civil avenues to protect herself and her children:

Legal Separation: Allows the couple to live apart and dissolve the absolute community of property, but it does not allow them to remarry. Infidelity (sexual infidelity or perversion) is a valid ground.
Petition for Support: Under the Family Code, a husband is mandated to provide financial support to his wife and children. If he diverts funds to a mistress, the court can issue a support order and even attach his salary.
Declaration of Nullity (Article 36): If the infidelity is a symptom of a deeper "Psychological Incapacity" to comply with essential marital obligations that existed at the time of the celebration of the marriage, a petition for nullity may be filed.

4. Key Evidence and Limitations

To build a case, the following are often utilized:

Documentary Evidence: Birth certificates of illegitimate children, lease contracts in the husband's name for a different residence, or social media posts showing a public relationship.
Testimonial Evidence: Affidavits from neighbors or witnesses who can swear to the cohabitation.

The "Pardon" Rule

In both Adultery and Concubinage, the case cannot be pursued if the offended party has consented to the offense or pardoned the offender. A "pardon" can be express or implied (e.g., continuing to live and sleep with the husband after discovering the affair).

Summary Table

Legal Basis	Applicable To	Main Requirement
Concubinage	Husband	Proof of cohabitation, scandalous sex, or keeping mistress in the home.
RA 9262 (VAWC)	Husband/Partner	Proof of emotional/psychological distress caused by the infidelity.
Legal Separation	Both	Proof of sexual infidelity (civil case).

Would you like me to draft a summary of the specific documents needed to file a VAWC complaint for psychological distress?