Short answer. No. Article 833 of the Civil Code provides that a revocation of a will based on a false cause is null and void. If your father revoked his will because he believed something that was not true, and that false belief was the reason for the revocation, the revocation has no legal effect.
What the law says
A revocation of a will based on a false cause or an illegal cause is null and void.
Civil Code, Article 833 — Revocation on a False Cause. Read the full provision →
The rule against revocations on false causes
Article 833 of the Civil Code states plainly: A revocation of a will based on a false cause or an illegal cause is null and void. The article recognizes two separate grounds for invalidating a revocation: a false cause and an illegal cause. A revocation based on a false cause is one where the testator's stated or real reason for revoking — the motive that drove the act — was factually untrue. If your father revoked his will because he believed your sibling had defrauded him, and that belief was false, then the revocation rests on a false cause and is null and void.
What makes a cause false
A cause is false when the fact stated or believed by the testator as the reason for the revocation did not actually occur or was factually incorrect. The false cause must be the reason the testator revoked — it must have been the motivation that drove the act of revocation. If the testator would have revoked the will anyway, regardless of the false belief, then the false cause did not actually cause the revocation and Article 833 may not apply to void it. But if the false belief was genuinely what motivated the testator to revoke — if he would not have revoked but for that false belief — then the revocation is void.
What this means for the original will
If the revocation is null and void, it has no legal effect. A null revocation is treated as if it never happened. The will that was purportedly revoked remains valid and in force as if the revocation had never been made. Your father's original will — the one he intended to revoke — would therefore still be his last valid will. For the affected heirs, this is significant: the provisions of the original will continue to govern the distribution of the estate, not whatever would happen as a result of the revocation (whether that is intestate succession or a new will, if any).
How to establish the false cause
Establishing that a revocation was based on a false cause requires showing two things: first, that the stated or underlying reason for the revocation was factually untrue; and second, that this false reason was actually the cause of the revocation. Evidence of the testator's stated reason at the time of revocation — through witnesses, notarial records, letters, or the revocation document itself — is relevant. Evidence that the belief was incorrect — that the fraud or other event the testator believed had occurred actually did not — is also essential. The burden of establishing that the revocation rests on a false cause falls on the party seeking to have the revocation declared void.