1) Why “illegitimacy” still matters in inheritance

Philippine law substantially protects children regardless of the circumstances of their birth, but it still maintains the categories legitimate and illegitimate for family relations and succession (inheritance). The difference shows up most sharply in:

Compulsory heir status (whether the law reserves a minimum share for you),
The size of your reserved share (legitime), and
Who you can inherit from by intestacy (no will), especially because of the “iron curtain” rule.

Core sources are the Civil Code provisions on Succession (Book III) and the Family Code provisions on Filiation, especially Family Code Article 176 on the legitime of illegitimate children.

2) Who is an “illegitimate child” for inheritance purposes

2.1. General rule

A child is illegitimate if conceived and born outside a valid marriage, unless the child is later legitimated or otherwise treated by law as legitimate.

2.2. Important “status-changing” situations

Because inheritance depends on status, these doctrines matter:

Legitimation (Family Code, Arts. 177–182) If the parents were not disqualified to marry each other at the time of the child’s conception, and they later validly marry, the child may be legitimated—and is treated as legitimate for inheritance (full legitimate-child shares, and no “iron curtain” limitations as between legitimate relatives).
Adoption A legally adopted child generally becomes, for succession purposes, a child of the adopter(s) with the status and rights the adoption law confers (commonly treated as a legitimate child of the adopter). This can expand inheritance rights in the adoptive family and change rights vis-à-vis the biological family depending on the adoption framework.
Children born of certain void/voidable marriage situations Some children are deemed legitimate by law despite issues affecting the parents’ marriage. This can radically alter inheritance rights and should be checked case-by-case under the Family Code’s legitimacy provisions.

3) The first gate: proving filiation (paternity/maternity)

Inheritance rights require proof of filiation—you must first establish that you are legally recognized as the decedent’s child.

3.1. Common proof

Illegitimate filiation may be proven through mechanisms recognized under the Family Code and evidence rules, such as:

Record of birth / birth certificate showing the parent,
A written acknowledgment (public or private documents),
Open and continuous possession of the status of a child (consistent treatment as a child), and
Other admissible evidence, including DNA evidence under Supreme Court rules on DNA evidence.

3.2. Why this matters in practice

In estate settlements, an alleged illegitimate child who is not clearly acknowledged often must first litigate filiation (or raise it in an estate proceeding), before successfully claiming a share.

4) Illegitimate children as compulsory heirs

4.1. Compulsory heir status

Illegitimate children are compulsory heirs of their parents. Being a compulsory heir means:

The law reserves for you a minimum share called the legitime, and
Any will, donation, or partition that impairs your legitime can be reduced to complete it.

4.2. The key rule on size of legitime (Family Code, Art. 176)

As a baseline principle, the legitime of an illegitimate child is one-half of the legitime of a legitimate child.

This “half-share” idea appears repeatedly in succession computations and is the starting point for understanding how illegitimate children share with other heirs.

5) Two different worlds: testate vs intestate succession

Inheritance outcomes depend heavily on whether there is a valid will.

5.1. Testate succession (there is a will)

The estate is divided into:
- Legitime (reserved for compulsory heirs), and
- Free portion (the part the decedent can generally give away by will, subject to legitimes).
Illegitimate children must receive at least their legitime.
Beyond the legitime, the decedent may give an illegitimate child more (from the free portion), as long as the legitimes of other compulsory heirs are not impaired.

5.2. Intestate succession (no will, or will is ineffective as to the whole estate)

The entire net estate is distributed by law among the legal heirs.
Illegitimate children may receive more than their legitime in intestacy because there is no free portion being directed elsewhere; the estate goes to heirs under intestacy rules.

6) What illegitimate children can inherit from (and from whom they cannot)

6.1. They inherit from their parents

An illegitimate child can inherit from the mother and the father, as long as filiation is established.

6.2. The “iron curtain” rule (Civil Code, Art. 992)

A crucial limitation in intestate succession is the Civil Code’s “iron curtain” rule:

An illegitimate child has no right to inherit by intestacy from the legitimate children and legitimate relatives of his/her father or mother; and
Those legitimate children/relatives likewise cannot inherit by intestacy from the illegitimate child.

Practical meaning: Even if you are undeniably the decedent’s child, this rule can block intestate inheritance between you and the decedent’s legitimate relatives (for example: legitimate half-siblings, legitimate grandparents, legitimate uncles/aunts), depending on the family structure.

Important boundary: This rule is about intestate succession. It does not prevent someone from giving property to an illegitimate relative by will, or through inter vivos transfers, subject to legitime rules.

7) How shares commonly work (conceptual guide + common patterns)

7.1. A reliable “ratio” concept when legitimate and illegitimate children both inherit

When legitimate and illegitimate children inherit together (common in intestacy and often mirrored in minimum-share analysis), the organizing principle is:

Each illegitimate child’s share is generally pegged at one-half of a legitimate child’s share, subject to rules protecting the reserved shares of other compulsory heirs (e.g., legitimate children’s legitime cannot be impaired).

A practical way people visualize this is a 2:1 ratio:

Assign 2 parts to each legitimate child,
Assign 1 part to each illegitimate child, then divide the relevant distributable portion accordingly—while observing any fixed legitime protections and spouse/ascendant shares where applicable.

7.2. Common intestate outcomes involving illegitimate children

These are frequently encountered situations:

A) Only illegitimate children survive (no spouse, no legitimate descendants/ascendants)

All inherit in equal shares.

B) Legitimate children and illegitimate children survive (no spouse)

Shares follow the 2:1 concept: a legitimate child typically receives double the share of an illegitimate child.

C) Surviving spouse and illegitimate children survive (no legitimate descendants)

A commonly applied intestate pattern is: spouse shares with illegitimate children, with a fixed fraction for the spouse and the balance to illegitimate children, divided equally among them (this is governed by the Civil Code’s intestacy provisions on concurrence with the spouse).

D) Illegitimate children and legitimate parents/ascendants survive (no legitimate descendants)

Illegitimate children may share with legitimate ascendants under the intestacy rules, with the estate divided between the concurring classes as provided by the Civil Code.

(These patterns become more intricate once you add a surviving spouse plus ascendants plus illegitimate children, or when you introduce representation issues and questions of who exactly qualifies as an heir in the first place.)

7.3. Testate (will) minimum-share patterns involving illegitimate children

In wills, the decedent can distribute the free portion, but must respect legitimes. As a conceptual baseline:

Illegitimate children cannot be deprived of at least their legitime unless validly disinherited for a legal cause and with strict formal requirements.

8) Rights that protect illegitimate children against being “cut out”

8.1. Right to completion of legitime (reduction of inofficious dispositions)

If a will, donation, or settlement reduces an illegitimate child’s legitime, the illegitimate child may seek:

Reduction of excessive testamentary gifts (devises/legacies/institutions) and/or
Reduction of inofficious donations (inter vivos transfers) to the extent needed to complete the legitime.

8.2. Preterition (total omission) in a will

If a compulsory heir in the direct line is totally omitted from the will, it can trigger serious consequences for the will’s effectiveness as to institutions of heirs (depending on how the will is structured and whether the heir truly received nothing by any title). Illegitimate children, being compulsory heirs in the direct descending line, are commonly part of preterition disputes.

8.3. Collation and accounting (to make shares fair and lawful)

In estate computations, certain lifetime transfers to heirs may be brought into collation/accounting so that legitimes can be correctly computed and completed.

9) Disinheritance of an illegitimate child (and why it often fails)

An illegitimate child may be disinherited, but only if:

The disinheritance is made in a valid will,
It states a cause recognized by law, and
The cause is true and legally sufficient (and, if contested, capable of proof).

If disinheritance is defective in form or substance, the illegitimate child’s right to legitime can be restored.

10) Estate settlement problems where illegitimate children are most often deprived

10.1. Extrajudicial settlement without including the illegitimate child

A frequent scenario is an extrajudicial settlement executed by “known heirs” that excludes an illegitimate child. Depending on facts and timing, remedies may include:

Action to annul or set aside the settlement,
Action for partition and reconveyance, and/or
Protective measures like annotating claims where appropriate.

Sales to third parties in good faith can complicate recovery, making speed and evidence crucial.

10.2. Probate/administration proceedings

If there is a will or an ongoing judicial settlement:

An illegitimate child who claims heirship typically must appear and assert rights in the proceeding, and
If filiation is disputed, it may become a threshold issue for entitlement.

11) Frequently asked (and frequently litigated) questions

11.1. “Do I have inheritance rights if my father never supported or acknowledged me?”

Yes, potentially, but inheritance rights depend on proving filiation. Lack of support does not automatically erase inheritance rights.

11.2. “Can I inherit from my father’s legitimate parents (my grandparents) if he is my father?”

By intestacy, the iron curtain rule can block inheritance between an illegitimate child and the legitimate relatives of the parent. However, those relatives may still give property by will (subject to their own compulsory heirs’ legitimes).

11.3. “Does using my father’s surname automatically prove I’m his child for inheritance?”

No. Use of surname may be relevant, but inheritance hinges on legally recognized proof of filiation, not naming alone.

11.4. “If my parents later married, do I still inherit only as illegitimate?”

If the requirements for legitimation are met, the child can become legitimate for succession purposes and inherit with full legitimate-child rights.

12) The essential takeaways

Illegitimate children are compulsory heirs of their parents and are entitled to a legitime, with the central baseline that it is one-half of a legitimate child’s legitime (Family Code, Art. 176).
Inheritance rights depend first on proof of filiation; disputes often turn on documents, conduct, and admissible scientific evidence like DNA.
The iron curtain rule (Civil Code, Art. 992) is a major limitation in intestate succession, barring inheritance between illegitimate children and the legitimate relatives of the parent, though it does not bar transfers by will.
Illegitimate children can challenge wills, donations, and settlements that impair legitime, and can defeat defective disinheritance or improper exclusion in estate settlements.