I. Why this topic matters

In Philippine family law, a child’s status (legitimate, illegitimate, legitimated, adopted) affects surname, parental authority, support, and successional rights (inheritance and legitimes). When a person marries someone who already has an illegitimate child, two legal pathways are commonly asked about:

Legitimation – a change of status from illegitimate to legitimate by operation of law, but only in a specific situation.
Adoption (step-parent adoption) – a court/administrative process that creates a legal parent-child relationship between the step-parent and the child.

These are not interchangeable. In most “spouse’s illegitimate child” scenarios, adoption is the relevant mechanism, not legitimation.

II. Core legal framework (Philippine context)

Key sources include:

Family Code of the Philippines (Executive Order No. 209, as amended) – rules on legitimacy/illegitimacy, legitimation, parental authority, support, and related consequences.
Civil registry laws and rules – recording/annotation of births, marriages, and changes of civil status.
Adoption laws – historically R.A. No. 8552 (Domestic Adoption Act) and R.A. No. 8043 (Inter-Country Adoption Act); more recently, adoption has been streamlined under R.A. No. 11642, which created the National Authority for Child Care (NACC) and shifted many adoption processes to an administrative model (while some matters may still involve courts depending on the situation and implementing rules).

III. Key concepts you must get straight

A. “Illegitimate child”

A child is illegitimate when conceived and born outside a valid marriage of the parents, subject to presumptions and special rules.

General consequences under Philippine law:

Parental authority over an illegitimate child belongs primarily to the mother.
The child is entitled to support from both parents.
In inheritance, an illegitimate child generally has a legitime, but it is typically less than that of a legitimate child under the traditional rule.

(The precise effects can vary depending on the fact pattern, acknowledgments, and later changes in status.)

B. “Legitimation”

Legitimation is a legal process where an illegitimate child becomes legitimate because the child’s biological parents later validly marry, provided strict requirements are met.

C. “Adoption”

Adoption creates a legal parent-child relationship between the adopter and adoptee, usually making the adoptee the adopter’s child “for all intents and purposes”, with the rights and obligations of legitimacy, subject to specific statutory exceptions and rules.

D. “Spouse’s illegitimate child” (the typical real-life scenario)

This usually means:

A woman has an illegitimate child with a man who is not her eventual husband; she later marries someone else (the stepfather).
Or a man has an illegitimate child with a woman who is not his eventual wife; he later marries someone else (the stepmother).

In those common situations, the step-parent is not the biological parent. That single fact drives the legal outcomes: legitimation generally won’t apply, but step-parent adoption may.

IV. Legitimation in detail (Family Code)

A. When legitimation is possible

Legitimation happens only when:

The child was conceived and born outside marriage; and
The child’s biological parents subsequently enter into a valid marriage; and
At the time of the child’s conception, the biological parents were not disqualified from marrying each other.

That third requirement is crucial. If, at conception, there was a legal impediment that made the parents unable to marry each other (for example, one parent was still married to someone else), legitimation is not available, even if they later marry after the impediment is removed.

B. The “spouse’s illegitimate child” problem: why legitimation usually does not work

If a person marries someone who already has an illegitimate child with another partner, the new spouse is not the child’s biological parent. Legitimation requires the subsequent marriage of the biological parents, not the marriage of the mother (or father) to a third person.

So, as a general rule:

A stepfather cannot legitimate his wife’s illegitimate child (if he is not the biological father).
A stepmother cannot legitimate her husband’s illegitimate child (if she is not the biological mother).

Legitimation is therefore relevant only when the spouse is marrying the child’s other biological parent (e.g., the man marrying the child’s mother is the child’s biological father, or vice versa), and the legal requisites are satisfied.

C. Effects of legitimation

When validly accomplished, legitimation:

Makes the child legitimate, as if legitimate from birth (a retroactive effect is recognized in principle).
Confers the rights of a legitimate child, including in general:
- Stronger status in family relations,
- Full parental authority structure applicable to legitimate children,
- Successional rights consistent with legitimacy,
- Use of the father’s surname consistent with the rules for legitimate children (implemented through civil registry annotation).

D. Civil registry and practical documentation (high-level)

In practice, legitimation must be properly recorded/annotated in the civil registry (Local Civil Registrar and PSA processes). Common documentary anchors include:

Birth certificate of the child,
Marriage certificate of the biological parents,
Acknowledgment/recognition documents when applicable,
Proper petitions/affidavits and registry compliance.

V. Adoption of a spouse’s illegitimate child (Step-parent adoption)

A. Why adoption is the typical solution

When the new spouse is not the biological parent, and the family wants the child to have:

A legally recognized parent-child relationship with the step-parent,
The step-parent’s surname (where desired and lawful),
Stronger rights to support and inheritance from the step-parent,
Unified parental authority within the household,

Step-parent adoption is the mechanism designed for this.

B. Who may adopt: the “spouses must adopt jointly” rule and its exceptions

Philippine adoption policy generally prefers joint adoption by spouses, but the law recognizes exceptions—one of the most important being:

One spouse may adopt the child of the other spouse (commonly called step-parent adoption).

This is exactly the “spouse adopting a spouse’s illegitimate child” scenario.

C. Best-interest-of-the-child standard

Adoption is not a private contract; it is a status-changing legal act governed by the principle that the child’s best interests are paramount. Even if all adults agree, the State still evaluates:

The adopter’s fitness,
The stability of the home,
The child’s situation and wishes (where age-appropriate),
Whether adoption is being used for improper ends (e.g., to defeat rights, evade obligations, or manipulate status without genuine parenting intent).

D. Consent requirements (the make-or-break issue in step-parent adoption)

Consent is central and fact-sensitive. Common consent considerations include:

The spouse-parent (the child’s biological parent who is married to the adopter)
- Typically must consent.
The other biological parent (the one not married to the adopter)
- Often required if legally identifiable and with legally recognized parental ties, unless the law allows dispensation due to circumstances such as:
  - Unknown identity,
  - Abandonment,
  - Death,
  - Deprivation/termination of parental authority,
  - Other legally sufficient grounds under applicable adoption rules.
The child’s consent
- Usually required once the child reaches a threshold age (commonly 10 years old in many Philippine family-law contexts), and also considered even when not strictly required, depending on rules and the child’s maturity.

Because illegitimate children typically fall under the mother’s parental authority by default, people sometimes assume the father’s consent is never needed. That assumption can be wrong in adoption practice if the father is known and has recognized ties, or if specific rules require notice/consent to protect due process and the child’s welfare.

E. What adoption changes: legal effects

When a step-parent adoption is granted/approved:

Creates a legal parent-child relationship between the step-parent and child
- The adopter becomes a legal parent with rights and duties (support, parental authority, representation, etc.).
Parental authority structure becomes unified
- The household typically gains a clearer two-parent legal framework (the spouse-parent and the adoptive step-parent).
Surname
- The child may take the adopter’s surname in accordance with the adoption order/approval and civil registry implementation.
Succession/inheritance
- The child generally gains inheritance rights from the adoptive parent as a child would.
- As to inheritance from the non-custodial biological parent: adoption rules generally sever legal ties with biological parents except where the biological parent is the spouse of the adopter (so ties to the spouse-parent remain). This can significantly affect inheritance rights, and families should understand that adoption is not merely a name-change; it restructures legal kinship.
Support obligations
- The adoptive parent becomes obligated to support the child as a parent.

F. Rescission/revocation and stability of status

Philippine adoption policy emphasizes permanence. Traditionally:

Adoption is not meant to be easily undone.
Grounds and who may initiate rescission/revocation are typically limited (often oriented to protect the child, not the adopter’s convenience).
The adopter’s remedies, when problems arise, are usually handled through family law mechanisms (including disciplinary measures and, in severe cases, disinheritance rules), rather than casually reversing the adoption.

Exact procedures depend on the governing adoption law and current implementing rules.

VI. Choosing between legitimation and adoption: a decision map

A. When legitimation is the correct route

Legitimation fits when all are true:

The person marrying the child’s mother/father is the child’s other biological parent;
The biological parents’ marriage is valid;
At the time of conception, the biological parents were not disqualified to marry each other.

B. When adoption is the correct route

Step-parent adoption fits when:

The spouse who wants legal parenthood is not the biological parent; and
The family wants the step-parent to be the child’s legal parent, with full parental rights and obligations.

C. When neither route is straightforward

Some common complications:

Adulterous conception / impediment at conception
- Legitimation may be barred because the biological parents were disqualified to marry at conception.
Absent/unknown/uncooperative other biological parent
- Adoption may still be possible, but consent/notice issues become the central legal battleground.
The child is already an adult
- Adult adoption has its own rules and policy concerns; “best interest” is still relevant, but the framework differs.
Purpose is primarily immigration, inheritance engineering, or document convenience
- Authorities scrutinize motivation; adoption is about establishing genuine parenthood consistent with welfare, not merely producing paperwork advantages.

VII. Intersections with related Philippine rules (often misunderstood)

A. Using the father’s surname (distinct from legitimation/adoption)

Philippine law has allowed mechanisms for an illegitimate child to use the father’s surname under certain conditions (commonly tied to acknowledgment). This is not the same as legitimation and does not automatically make the child legitimate.

So:

Name use can sometimes change without changing legitimacy.
Legitimation/adoption changes status, not merely the name.

B. Parental authority over illegitimate children

Because the mother generally has parental authority over an illegitimate child, day-to-day custody may already be stable within the new marriage. But without adoption, the step-parent usually remains a legal stranger in many formal contexts (school decisions, medical consent authority in strict settings, travel documentation, succession, and long-term support obligations).

C. Support

Support is a right of the child. Biological parents have support duties regardless of legitimacy. Adoption adds a new support obligor (the adoptive parent) and may affect how obligations are enforced and allocated.

D. Succession and legitimes

Status affects legitimes and intestate succession. Families frequently underestimate how strongly adoption restructures inheritance rights—especially regarding the child’s legal relationship to the non-spouse biological parent.

VIII. Practical outcomes and typical objectives (what families usually want)

A. “We want the step-parent to be the real legal parent.”

This is step-parent adoption, provided consents and welfare findings are satisfied.

B. “We want the child to become legitimate because we’re now married.”

Marriage to a step-parent does not legitimate the child. Legitimation requires the marriage of the biological parents, plus the “no disqualification at conception” requirement.

C. “We want a unified family name.”

That may be achievable through step-parent adoption, and in some cases through surname-use mechanisms for illegitimate children—each has different requirements and consequences.

D. “We want the child to inherit like a legitimate child from the step-parent.”

That is a core legal effect of adoption: it creates a parent-child relationship for inheritance purposes between adopter and adoptee, subject to the adoption law’s specific terms and exceptions.

IX. Summary of the big rules (Philippines)

Legitimation is narrow: it applies only when the biological parents later validly marry, and they were not disqualified to marry at the child’s conception. A step-parent cannot legitimate a child who is not biologically theirs.
Step-parent adoption is the primary legal pathway for a spouse to become the legal parent of the other spouse’s illegitimate child.
Consent and the child’s welfare govern adoption outcomes; the other biological parent’s status (known/unknown, present/absent, with or without legally recognized ties) often determines difficulty.
Adoption is a status transformation with far-reaching effects on parental authority, support, surname, and inheritance—not merely a paperwork exercise.