1) Governing Law and the Basic Rule

A. What “legitimation” is (Family Code, Arts. 177–182)

In Philippine family law, legitimation is the process by which a child who is illegitimate becomes legitimate by operation of law because the child’s biological parents subsequently contract a valid marriage, provided that at the time of the child’s conception, the parents were not disqualified by any legal impediment to marry each other.

The Family Code provisions commonly cited on legitimation are:

Art. 177 (who may be legitimated; core requisites),
Art. 178 (children who may be legitimated include those conceived and born before the marriage),
Art. 179–181 (effects/retroactivity and non-prejudice to vested rights),
Art. 182 (impugnation rules).

B. Why “nullity then subsequent marriage” complicates legitimation

A declaration of absolute nullity declares a prior marriage void from the beginning. Yet Philippine law also enforces the policy that marital status cannot be treated as void by mere private decision; capacity to remarry is tightly regulated (notably Art. 40, Family Code, requiring a judicial declaration of nullity before remarriage). This tension is most visible when a child was conceived while a parent was still in a prior marriage that was later declared void.

2) Distinctions That Decide Outcomes

A. Legitimacy vs. illegitimacy (Family Code, Arts. 164–167; 175–176)

A child is legitimate if conceived or born during a valid marriage, subject to the presumptions and rules on legitimacy.
A child is illegitimate if conceived and born outside a valid marriage, subject to rules on recognition/filiation.

B. Void vs. voidable marriage (Family Code, Arts. 35–38; 45–47)

A void marriage is inexistent from the start (nullity).
A voidable marriage is valid until annulled (annulment); children conceived/born before annulment are generally treated as legitimate within that framework.

This matters because legitimation requires no impediment at conception—and an existing valid marriage at conception is a classic impediment.

3) Requisites of Legitimation (Family Code, Art. 177, in substance)

A child may be legitimated only if all of the following are satisfied:

The child was illegitimate before the marriage of the parents.
The child’s biological parents later enter into a valid marriage with each other.
At the time of conception, the parents were free to marry each other, meaning no legal impediment existed then.

The third element (“no impediment at conception”) is the make-or-break requirement in nullity + later marriage situations.

4) The “No Impediment at the Time of Conception” Requirement

A. What counts as an impediment

Common impediments include:

Existing marriage of either parent to another person (marital impediment).
Prohibited degrees of relationship (incestuous relationships and certain void relationships).
Lack of capacity that renders marriage void (e.g., age below what the law requires for a valid marriage).
Other grounds that make a contemplated marriage void.

If an impediment existed at conception, legitimation does not occur, even if the parents later become free to marry and do marry.

B. Where nullity creates the controversy

A declaration of nullity says the prior marriage was void from the beginning. The conceptual argument is:

If the prior marriage was never valid, then there was no marital impediment at conception.

But Philippine family law also imposes the rule that:

A judicial declaration of nullity is required before a person may validly remarry (Family Code, Art. 40).

This creates two practical/legal pressures in opposite directions:

Retroactivity logic (void ab initio): the prior marriage is treated as never having existed as a valid marriage.
Stability/administrability logic (Art. 40 policy): society and the civil registry cannot treat someone as unmarried without a court declaration; otherwise, parties could self-judge their status.

In legitimation disputes, the question becomes: Does the “no impediment at conception” test look only at the objective invalidity of the prior marriage, or does it also account for the legal regime that treats the prior marriage as an impediment until a judicial declaration is obtained?

A cautious, practice-oriented approach tends to anticipate resistance (especially at the civil registry level) when conception occurred while one parent was still “married” in records and in social/legal reality, even if later declared void.

5) The Key Timeline: Conception, Not Birth

Legitimation hinges on conception, not just birth. Conception date is usually inferred medically from gestational age counted backward from birth, and in disputes it may be proven through:

medical records (prenatal care, ultrasound dating),
testimony and circumstantial evidence,
and, where necessary, scientific evidence in related filiation proceedings.

A mismatch between:

birth date (which is fixed on the civil registry) and
conception window (which determines impediments) is a common source of error in legitimation assessments.

6) Typical Scenarios in “Nullity + Subsequent Marriage” Cases

Scenario 1: Prior marriage later declared void; child conceived with new partner before the nullity judgment; parents marry after nullity

Issue: Was there an impediment at conception?

If prior marriage was voidable (annulment): impediment at conception is clear because the marriage was valid until annulled → no legitimation.
If prior marriage was void (nullity): arguments diverge:
- For legitimation: prior marriage void ab initio → no impediment in strict theory.
- Against/complicating: Art. 40 policy and the presumption/stability of marital status may be invoked to treat the situation as one involving a practical/legal impediment at conception, especially when records show an existing marriage and no judicial declaration yet.

Risk profile: high; often contested or administratively difficult.

Scenario 2: Prior marriage was voidable; child conceived before annulment; parents marry after annulment

At conception, there was a valid marriage → impediment → no legitimation.

Scenario 3: Both parents were free to marry at conception; child conceived/born; parents later marry

Classic legitimation → yes, child becomes legitimate upon the subsequent valid marriage.

Scenario 4: Final nullity judgment obtained before conception; child conceived afterward; parents later marry

At conception, no marital impediment from the prior marriage → legitimation is generally available (assuming the subsequent marriage is valid and filiation is established).

Scenario 5: Child conceived after the parents’ valid marriage

Child is legitimate by origin; legitimation is unnecessary.

7) Effects of Legitimation (Family Code, Arts. 179–181, in substance)

When legitimation applies:

Status: the child becomes legitimate.
Retroactivity: legitimation generally produces effects as if the child were legitimate from birth, but
Protection of vested rights: legitimation cannot prejudice vested rights acquired by third persons before legitimation (a critical limitation in succession/property disputes).
Parental authority: aligns with the incidents of legitimate filiation.
Name/surname and civil registry: records should be annotated/corrected to reflect legitimation.
Succession: legitime/intestate shares and other succession incidents follow the rules for legitimate children.

8) Legitimation Compared With Other Remedies

A. Proof/recognition of filiation (Family Code, Arts. 172–175; and related rules)

Even where legitimation fails, the child may still enforce rights through filiation:

recognition by the father (where legally sufficient),
or judicial action to establish filiation if contested.

This is often the practical route to secure:

support,
inheritance rights of an illegitimate child,
and appropriate entries in civil records.

B. Surname of illegitimate children (Family Code, Art. 176; and implementing laws)

If legitimation is unavailable, surname issues may still be addressed under the rules for illegitimate children, including the legal framework that allows use of the father’s surname under specified conditions.

C. Adoption

Adoption is not legitimation. It creates a new legal filiation (and typically confers legitimate status with respect to adoptive parents), subject to adoption law requirements and best-interest standards.

9) Civil Registry Implementation: How Legitimation Is Reflected on Records

Even when legitimation is “by operation of law,” families usually need the civil registry to reflect the change, because many downstream transactions rely on PSA-issued documents.

Common documentation in practice includes:

Child’s PSA birth certificate / local birth record.
Parents’ PSA marriage certificate (their subsequent marriage).
Proof of identity.
When relevant, finality documents for the nullity judgment affecting capacity to marry (decision, entry of judgment, certificate of finality).

Depending on the local civil registrar’s posture and the case facts, the registrar may:

process annotation through administrative steps, or
require a judicial order when changes are substantial, disputed, or legally sensitive.

10) Impugnation of Legitimation (Family Code, Art. 182, in substance)

Legitimation may be challenged only by those who are prejudiced in their rights by it, and it is subject to statutory limits on who may file and when (commonly framed around a limited prescriptive period from accrual of the cause of action). This becomes important in inheritance conflicts where legitimation changes compulsory heir status and shares.

11) A Practical Analytical Checklist for Lawyers and Parties

Confirm biological parentage (filiation) of both parents.
Compute conception window and align it with parents’ civil status at that time.
Classify the prior marriage issue:
- void (nullity) vs voidable (annulment),
- ground and legal consequences relevant to capacity.
Test “no impediment at conception” against the timeline.
Validate the subsequent marriage of the biological parents.
Assess registry feasibility:
- likely administrative annotation vs likely need for court action.
Assess collateral consequences (succession, benefits, prior settlements, vested rights).

12) Working Takeaway

Legitimation in the Philippines is strict and technical: subsequent valid marriage of the biological parents is not enough unless it is paired with the decisive condition that no legal impediment existed at conception. In “nullity + later marriage” fact patterns, the central friction lies between (1) the retroactive theory of void marriages and (2) the legal policy requiring judicial confirmation of nullity for purposes of civil status stability and remarriage regulation. The legally safest outcomes occur when the nullity judgment predates conception, or when the parents were otherwise clearly free to marry at conception; the most contested cases are those where conception occurred while one parent remained in a prior marital status that was only later judicially declared void.