Short answer. Infidelity is not named in Article 921 as such. The route is the fourth cause — that the spouse has given cause for legal separation — because sexual infidelity is one of the grounds for legal separation under the Family Code. The will must specify the cause.

What the law says

When the spouse has given cause for legal separation

Civil Code, Article 921 — Grounds to Disinherit a Spouse. Read the full provision →

What the law says

A subsequent reconciliation between the offender and the offended person deprives the latter of the right to disinherit, and renders ineffectual any disinheritance that may have been made.

Civil Code, Article 922 — Reconciliation Wipes Out Disinheritance. Read the full provision →

What the article actually lists

The following shall be sufficient causes for disinheriting a spouse: (1) When the spouse has been convicted of an attempt against the life of the testator, his or her descendants, or ascendants; (2) When the spouse has accused the testator of a crime for which the law prescribes imprisonment of six years or more, and the accusation has been found to be false; (3) When the spouse by fraud, violence, intimidation, or undue influence cause the testator to make a will or to change one already made; (4) When the spouse has given cause for legal separation. The list ends with the loss of parental authority and the unjustifiable refusal to support. Adultery and concubinage appear nowhere in it by name.

The fourth cause is the doorway

Cause (4) does not require a decree, or even a filed case — it asks whether the spouse has given cause for legal separation. Article 55 of the Family Code opens A petition for legal separation may be filed on any of the following grounds: and its eighth ground is sexual infidelity or perversion. So everything turns on the wording: a will that says 'because he was unfaithful' cites something Article 921 does not list, while one saying the spouse has given cause for legal separation by sexual infidelity cites the recognised ground and identifies the conduct relied on.

Form, and who must prove it

Article 916 permits disinheritance only through a will in which the legal cause is specified, so this cannot be handled by a separate letter or an affidavit left with the family. Article 917 then places the burden of proving the truth of the cause on the other heirs if the disinherited spouse denies it — and the testator will not be there to testify. The evidence therefore has to exist independently of the deceased's own account. Article 918 sets the price of failure: a cause not specified, not proved, or not one the Code lists annuls the institution of heirs insofar as it prejudices the person disinherited.

Reconciliation, and what happens if it fails

The most common way one of these clauses dies is not a legal argument but a change of heart. A subsequent reconciliation between the offender and the offended person deprives the latter of the right to disinherit, and renders ineffectual any disinheritance that may have been made. A couple who resume living together after the will is signed will generally have destroyed it on this point. And where the disinheritance fails for any reason, the surviving spouse is a compulsory heir again: Article 904 provides that the testator cannot deprive compulsory heirs of their legitime except in cases expressly specified by law.

Cases citing this provision

These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.

Related provisions

Note. Statute text quoted on this page is reproduced from the official enactment and is linked to the full provision. The explanation around it is general legal information from Vivas & Nobles Law Office, not legal advice. Whether it applies to your situation depends on facts only a lawyer reviewing them can assess.