Below is a comprehensive discussion of inheritance rights of legitimate and illegitimate children under Philippine law. This write-up focuses on the key legal provisions, doctrinal rulings, and practical implications as they relate to succession (inheritance) in the Philippines.

1. Governing Laws and Sources

Civil Code of the Philippines (Republic Act No. 386) – Contains the basic rules on succession, including who are compulsory heirs, how the estate is divided, and the legitimes (the portion of an estate that the law reserves for compulsory heirs).
Family Code of the Philippines (Executive Order No. 209, as amended) – Governs matters of personal and family relations, including the rules on legitimacy or illegitimacy of children.
Republic Act No. 9255 – Amended certain provisions of the Family Code regarding surname use of an illegitimate child, though it does not directly change the rules on inheritance shares, it remains relevant because it emphasizes recognition of illegitimate children.
Jurisprudence – The Supreme Court decisions interpreting statutes on family and succession law.

2. Definitions of Legitimate and Illegitimate Children

2.1. Legitimate Children

Under Article 164 of the Family Code, children conceived or born during a valid marriage, or those born within 300 days after the marriage has been terminated (and before the mother has contracted a subsequent marriage), are presumed legitimate.

2.2. Illegitimate Children

Under Article 165 of the Family Code, children conceived and born outside a valid marriage are considered illegitimate (e.g., born of parents who were never married or born of an adulterous relationship). Even if recognized by the father, the child remains “illegitimate” unless certain legal requirements are met to alter status (but these typically involve adoption rather than retroactive changes in filiation status).

3. Compulsory Heirs Under Philippine Law

3.1. Who Are Compulsory Heirs?

Article 887 of the Civil Code enumerates the compulsory heirs:

Legitimate children (and their descendants)
Legitimate parents (and ascendants, in default of legitimate children)
The surviving spouse
Illegitimate children
In certain instances, acknowledged natural children and other illegitimate children under older laws, but effectively covered now by “illegitimate children”

Both legitimate and illegitimate children are compulsory heirs. This means the law reserves for them a portion of the deceased’s estate (the legitime), which cannot be diminished by will. The main difference, however, is in the amount of their respective shares.

4. Primary Difference in Inheritance Shares

4.1. Share of a Legitimate Child

By default, legitimate children (when they are the only heirs together with or without a surviving spouse) are entitled to equal shares of the legitime portion.

4.2. Share of an Illegitimate Child

Under Article 176 of the Family Code (as renumbered and amended by R.A. 9255, but the principle on inheritance is found in the Civil Code) and relevant jurisprudence, the share of an illegitimate child is half that of a legitimate child. This is the statutory rule that remains in effect despite certain discussions on equal protection. Thus, if one legitimate child gets “1 share,” an illegitimate child would be entitled to “1/2 share” in the same distribution scenario.

4.3. Example

Suppose a deceased parent is survived by:

One (1) legitimate child; and
One (1) illegitimate child.

If the net distributable estate (for the legitime portion) is PHP 1,200,000, the distribution would generally be:

Legitimate child: PHP 800,000 (which is the “1 share”)
Illegitimate child: PHP 400,000 (which is “1/2 share”)

In other words, for every full share a legitimate child receives, an illegitimate child receives half of that amount.

5. Intestate Succession vs. Testate Succession

5.1. Intestate Succession

When a person dies without leaving a valid will, his or her estate is distributed according to the rules of intestacy under the Civil Code. In that scenario:

The children (legitimate or illegitimate) are called to inherit together.
Their shares follow the rule: “Illegitimate children receive half of the portion a legitimate child would receive.”

5.2. Testate Succession

When a person dies with a will, the law still mandates that compulsory heirs must receive their legitimes, which cannot be diminished or taken away by the testator’s dispositions. The testator may allocate the free portion of the estate in any manner, but the legitime rules remain:

Legitimate children collectively receive at least one-half of the total estate as their legitime (subject to further division among them).
Illegitimate children, as compulsory heirs, must likewise receive their mandatory shares (half that of each legitimate child’s share).

No matter what the will states, these shares cannot be invalidated or reduced below the minimum guaranteed by law.

6. Recognition and Proof of Filiation

6.1. Importance of Recognition

An illegitimate child must generally be acknowledged or recognized to enforce inheritance rights against the father’s or mother’s estate. Recognition can be:

Voluntary – In a will, a public document, or an admission in official records.
Involuntary/Compulsory – Proven via court action, DNA evidence, relevant documents (e.g., birth certificates signed by the parent), or other conclusive evidence of filiation.

6.2. Evidentiary Considerations

Birth Certificate: Listing the father’s name is strong proof of filiation if accompanied by the father’s signature or acknowledgment.
Court Action: If paternity or filiation is contested, an illegitimate child (or his/her representative) may file a petition for recognition in court.

Without recognition or proof of filiation, an alleged illegitimate child cannot claim inheritance from the putative parent’s estate.

7. Surname Use (RA 9255) vs. Inheritance Rights

Although Republic Act No. 9255 (amending Article 176 of the Family Code) allows illegitimate children to use their father’s surname under certain conditions, this does not affect or equalize their inheritance shares with those of legitimate children. The rule remains that the illegitimate child’s share is half that of a legitimate child.

In practice, however, use of the father’s surname often indicates recognition, which can bolster an illegitimate child’s right to claim inheritance. But the share differential persists unless new legislation modifies the Civil Code’s provisions.

8. Equal Protection and Constitutional Debates

8.1. Constitutional Provisions

The 1987 Philippine Constitution (Article II, Section 12) emphasizes the State’s duty to protect the family and children, whether legitimate or illegitimate. There have been academic and legislative debates questioning the constitutionality of giving different inheritance shares to illegitimate children.

8.2. Supreme Court Stand

To date, the Supreme Court has not categorically declared the “half share” rule unconstitutional. As it stands, the statutory rule is still enforceable, and courts continue to follow it. Attempts to amend or invalidate the distinction have not succeeded legislatively, meaning that the principle remains in effect.

9. Other Relevant Points

Adopted Children – Under Philippine law, an adopted child inherits as a legitimate child, effectively receiving the same share as a legitimate child. This does not cure illegitimacy per se but rather confers legal status akin to legitimate children for inheritance purposes.
Representation Rights – Legitimate and illegitimate children can be represented by their own descendants if they predecease the parent whose estate is in question. Representation follows the same ratio: if one is an illegitimate descendant, he or she steps into the shoes (and fraction) of the illegitimate ascendant.
Disinheritance – Certain strict conditions must be met to validly disinherit a compulsory heir. Disinheritance requires a will and a legal cause (enumerated by law). Simply labeling a child “illegitimate” is not a ground to disinherit. Because illegitimate children are still compulsory heirs, they cannot just be omitted unless valid disinheritance grounds exist.
Waiver of Rights – Illegitimate children, once recognized, may waive their inheritance rights, but such waiver must be done after the death of the parent. A waiver before the parent’s death is generally void for being a waiver of a future inheritance.
Accrual of Rights – Inheritance rights are enforceable only upon the death of the parent. During the parent’s lifetime, there is no vested right to a future estate share, aside from the intangible right to be recognized as a child for future inheritance.

10. Practical Implications and Tips

Documentation – Ensure proper registration of birth and recognition (e.g., affidavit of acknowledgment) to avoid lengthy court battles over proof of filiation.
Estate Planning – Parents who wish to provide more for their illegitimate children, or ensure smooth distribution, may do so through valid wills and donations, but the mandatory legitime of legitimate children cannot be impaired.
Court Proceedings – If recognition is challenged, expect that DNA testing and other evidence may be required. Litigating filiation issues can be time-consuming and costly.

11. Conclusion

In the Philippine legal system, both legitimate and illegitimate children are compulsory heirs, meaning the law protects their rights to a certain portion of the decedent’s estate. The critical difference is that an illegitimate child’s share is by law half of that of a legitimate child. This longstanding rule remains enforceable despite evolving social and legal perspectives on children born outside valid marriages. Unless and until Philippine legislation or jurisprudence significantly alters these provisions, the division of shares described above stands as the controlling principle in inheritance matters involving legitimate and illegitimate children.