Short answer. On exactly the same evidence a legitimate child uses: the record of birth or a final judgment, or an admission of filiation in a public document or a signed handwritten instrument. The difference is timing. Where the claim rests on the second-tier evidence, it must be brought during the alleged parent's lifetime.

What the law says

Illegitimate children may establish their illegitimate filiation in the same way and on the same evidence as legitimate children.

Family Code, Article 175 — How Illegitimate Filiation Is Established. Read the full provision →

What the law says

except when the action is based on the second paragraph of Article 172, in which case the action may be brought during the lifetime of the alleged parent

Family Code, Article 175 — How Illegitimate Filiation Is Established. Read the full provision →

No lesser standard of proof, and no separate one

The opening sentence does something quietly important: it refuses to build a second, weaker evidentiary regime for illegitimate children. The same way, the same evidence. So the hierarchy in Article 172 applies here too — first the record of birth in the civil register or a final judgment, and an admission of filiation in a public document or a private handwritten instrument signed by the parent; then, only where none of that exists, open and continuous possession of the status together with any other means allowed by the Rules of Court and special laws. What differs between legitimate and illegitimate filiation is not the proof. It is the clock.

The timing rule that decides most real cases

Where the action rests on the second paragraph of Article 172 — possession of status, or other means — it may be brought only during the lifetime of the alleged parent. That single clause closes the door on the most common scenario in Philippine practice: a child who was privately supported but never documented, coming forward once the father has died and an estate is being settled. If there is no birth record naming him and no signed handwritten acknowledgement, the route that remains is the one that had to be taken while he was alive. Delay here is not merely risky; it is often fatal to the claim.

The other period, for first-tier evidence

Where the claim does rest on first-tier evidence, the timing follows the general rule for claiming filiation: the action belongs to the child during his or her lifetime, and is transmitted to the heirs only if the child dies during minority or in a state of insanity, in which case the heirs have five years to bring it. So the practical picture is two very different exposures depending on what documents exist. A child holding a signed acknowledgement is in a materially stronger position than one holding twenty years of photographs, and the difference is not about credibility at all.

What to look for, and when to look

The search worth doing first is documentary and specific: the civil registry record of the birth and what it says about the father; any judgment in an earlier case; and any instrument in the parent's own handwriting, signed by him, that admits the relationship — a letter, a note, a form. Those are the items that lift a claim into the first tier. If none of them exists and the parent is living, that fact is itself the reason to take advice now rather than later, because the availability of the action is being measured against a life rather than against a fixed number of years.

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.