THE LEGAL DEFINITION OF ILLEGITIMATE CHILDREN IN THE PHILIPPINES (A comprehensive doctrinal and jurisprudential survey)

1. Statutory Definition

Under Article 165 of the Family Code of the Philippines (E.O. No. 209, 1987), “Children conceived and born outside a valid marriage are illegitimate, unless otherwise provided in this Code.” The negative phrasing (“unless otherwise provided”) is crucial, because subsequent articles (especially Arts. 163, 164, 172–176 & 177) and special statutes carve out important exceptions whereby a child born outside wedlock may still be deemed legitimate or later legitimated.

2. Who Is Not Illegitimate: Statutory Exceptions

Exception	Governing Provision	Effect
Good-faith void marriage (including psychological incapacity)	Art. 54(1), Family Code	If at least one spouse honestly believed the marriage was valid, children conceived or born before final judgment of nullity are legitimate.
Voidable marriage annulled	Art. 54(2)	Same rule of legitimacy while the marriage subsisted and until final judgment of annulment.
Subsequent valid marriage of parents	Art. 178, 179 (legitimation)	Natural children conceived and born outside wedlock of parents not suffering any impediment to marry at conception or birth become legitimated by the parents’ later valid marriage.
Legitimation by subsequent marriage for lack of license	R.A. 9858 (2009)	Children born to parents whose only impediment was the absence of a marriage licence are legitimated by the parents’ later civil wedding.
Administrative legitimation of simulated births	R.A. 11222 (2019)	A child whose birth record was simulated may, after compliance with the Act, be deemed legitimate.

Children who fall under these exceptions are not “illegitimate” despite being “born outside a valid marriage” in the ordinary sense.

3. Historical Evolution

Old Civil Code (Spanish-era, 1889) – distinguished natural, spurious and legitimate children, with sharp discrimination in inheritance.
New Civil Code (R.A. 386, 1950) – kept categories but softened disabilities; introduced legitimation by subsequent marriage.
Family Code (1987) – swept away the natural/spurious terminology, adopted the single term “illegitimate,” expanded legitimation, and gave mothers automatic parental authority.
Special statutes (R.A. 9255, 9858, 11222, plus amendments to the Civil Registry Law) continued the liberalization trend, reflecting the 1987 Constitution’s mandate that the State “shall defend the right of children to assistance … regardless of the circumstances of their birth.”

4. Proof of Filiation of an Illegitimate Child

Primary modes (Art. 172)

Record of birth appearing in the civil registry or final judgment;
Open and continuous possession of the status of a child; or
Other authentic writings (e.g., public instruments, private handwritten admission).

Secondary modes (Art. 175) – in their absence, filiation may be proved by:

testimony of credible witnesses;
DNA evidence (now routinely accepted in paternity/maternity cases);
circumstantial evidence that “leaves no room for doubt.”

Action must be brought within the child’s lifetime (Art. 173), but the child’s heirs may continue an already-filed case.

5. Surname, Parental Authority & Custody

Aspect	Default Rule	Notable Variations
Surname	Illegitimate child “shall use the surname of the mother.” (Art. 176)	R.A. 9255 (2004) allows use of the father’s surname if he expressly recognizes the child in a public instrument or sworn statement.
Parental authority & custody	Solely with the mother (Art. 176, first sentence).	Courts will transfer custody only if the mother is unfit, or the child (≥7 yrs.) chooses the father and the court finds the choice prudent.
Travel authority	DFA regulations generally require the mother’s consent for passports; father’s consent suffices only if child already uses his surname under R.A. 9255.

6. Support Obligations

Parents and illegitimate children owe each other support in proportion to resources and needs (Arts. 195, 201–203). The action for support may be joined with a filiation suit. Provisional support (pendente lite) is available upon prima facie showing of filiation.

7. Successional Rights and Legitimes

Heir	Legitime Share under Art. 895 (with legit. descendants)	Notes
Legitimate child	1 unit	Benchmark
Illegitimate child	½ unit (so 2 illegitimate = 1 legitimate)	The 1987 Family Code abolished the natural/spurious split but retained the ½ ratio.
Only illegitimate children surviving	Estate in equal shares (no discrimination among them).	Legitime = all, subject to legitime of surviving spouse or parents.

Important jurisprudence: Diaz v. Intermediate Appellate Court (G.R. L-66574, 1985) first applied the constitutional policy to succession. Heirs of Donato v. Badilla (G.R. 171107, 2011) reaffirmed that the ½ ratio is constitutional so long as illegitimate children are not totally disinherited.

8. Civil, Criminal & Labor-Law Incidents

Torts – A defamatory imputation that a person is “illegitimate” is not per se libelous, but context may still make it actionable.
Criminal law – For articles on seduction, abduction, rape (Arts. 337–338, 266-A RPC), legitimacy is irrelevant; parental consent may be required from the mother.
Labor & SSS/GSIS benefits – Illegitimate children expressly included in compulsory beneficiaries; proof of filiation under Art. 172 suffices.
Immigration/Derivative citizenship – Illegitimate child of a Filipino mother is a Philippine citizen jure sanguinis; if the Filipino parent is the father, recognition must precede the child’s 18th birthday (F.B. vs. COMELEC, G.R. 190022, 2010).

9. Legitimation and Acknowledgment in Practice

Legitimation by subsequent marriage (Arts. 178–179) produces effects retroactive to birth; no court order needed— annotation of the child’s birth record suffices.
Administrative acknowledgment – The “Affidavit of Admission of Paternity” (AAP) or “Affidavit to Use the Surname of the Father” (AUSF) under R.A. 9255 must be registered with the Local Civil Registrar.
Judicial approval remains necessary if the child is already 18 years old or if the mother refuses consent.

10. Intersection with Modern Family-Law Developments

Tan-Andal v. Andal (G.R. 196359, May 11 2021) liberalized nullity on psychological incapacity yet preserved the good-faith legitimacy rule, shielding children from the stigma of nullity.
Increasing acceptance of DNA testing simplifies proof of filiation, reducing litigation delays that historically harmed illegitimate children.
The Child and Youth Welfare Code and R.A. 11054 (Bangsamoro Organic Law) echo national rules, indicating nationwide uniformity despite autonomous regions.

11. Policy Trajectory & Reform Proposals

Scholars and legislators have repeatedly proposed full equality in legitimes, citing Article 3 of the U.N. Convention on the Rights of the Child and the 1987 Constitution’s social-justice clauses. Bills amending Art. 895 (e.g., House Bills 668 & 2263, 19th Congress) are pending; until enacted, the “½ ratio” endures.

Conclusion

In Philippine law, an illegitimate child is simply one “conceived and born outside a valid marriage” and not embraced by the Code’s exceptions that confer legitimacy. Over the last seventy-five years, statutes and jurisprudence have steadily narrowed that category—expanding legitimation, easing proofs of paternity, and strengthening economic rights—while some vestiges of differentiation (notably in inheritance) remain. Practitioners must therefore (1) locate the child within or outside the statutory exceptions, (2) establish filiation by the proper evidentiary modes, and (3) assert the full menu of rights—from names, custody and support to succession—secure in the constitutional command that “no child shall suffer discrimination in the safeguarding of its welfare, whether born in or out of wedlock.”