The Philippine Family Code (Executive Order No. 209, series of 1987, as amended), which became effective on 3 August 1988, establishes the legal framework for filiation, parental authority, support, and related family relations. While succession proper remains governed by Book III of the Civil Code of the Philippines (Republic Act No. 386), the Family Code fundamentally determines who qualifies as a “child” entitled to inheritance rights. It abolished the earlier distinctions among natural, acknowledged natural, and spurious children, replacing them with the simpler binary of legitimate and illegitimate children. This reform expanded the rights of children born out of wedlock, yet preserved distinctions in inheritance shares that reflect the Code’s balance between parental autonomy and the protection of the family as an institution.

I. Determination of Legitimacy and Illegitimacy

Article 163 of the Family Code classifies natural filiation as either legitimate or illegitimate. Article 164 declares that children conceived or born during the valid marriage of the parents are legitimate. Article 165, in turn, states that children conceived and born outside a valid marriage are illegitimate. The presumption of legitimacy under Article 164 is strong and may be impugned only by the husband or his heirs within the periods and on the grounds specified in Articles 166 to 170.

Special rules apply to children born from marriages that are later declared void or annulled. Under Article 54, children conceived or born before the judgment of annulment or nullity of a marriage under Article 36 (psychological incapacity) or other voidable grounds are considered legitimate. Children born from marriages that are void ab initio under Articles 35, 37, or 38 (e.g., bigamous, incestuous, or against public policy) are generally illegitimate unless conceived or born prior to the judicial declaration and falling under the protective clause of Article 54. In all cases, the status is fixed at the moment of conception or birth for inheritance purposes.

II. Establishment of Filiation as a Prerequisite to Inheritance Rights

No inheritance rights accrue unless filiation is established. Article 172 enumerates the modes of proving filiation:

For voluntary recognition of an illegitimate child: (1) a record of birth appearing in the civil registry in which the father or mother acknowledges the child; (2) an admission of filiation in a public document; or (3) a private handwritten instrument signed by the parent concerned.

Recognition may be made by the father, the mother, or both. Republic Act No. 9255 (2004), which amended Article 176, further allows an illegitimate child to use the surname of the father upon recognition through any of the foregoing means or upon final judgment in a judicial action.

In the absence of voluntary recognition, Article 175 authorizes a judicial action to establish filiation. The action may be brought by the child during his or her lifetime and, in exceptional cases, by the heirs within the periods prescribed by Article 173. The burden of proof rests on the claimant, who may present any competent evidence, including DNA testing as accepted in Philippine jurisprudence.

III. General Rights Flowing from Recognized Filiation

Once filiation is established, an illegitimate child enjoys rights to support (Articles 194–208), use of surnames (as amended), and, in appropriate cases, parental authority and custody. These rights are relevant to inheritance because they confirm the parent-child relationship that triggers succession rules. The Family Code places illegitimate children on equal footing with legitimate children with respect to support and personal status, but defers to the Civil Code for the quantitative aspects of inheritance.

IV. Inheritance Rights Proper: Compulsory Heir Status and Legitime

Article 887 of the Civil Code lists illegitimate children among the compulsory heirs. They cannot be totally disinherited except for the causes enumerated in Article 919. Their legitime—the portion of the estate reserved by law—is governed by Article 895 of the Civil Code: the legitime of each illegitimate child consists of one-half of the legitime of a legitimate child.

Computation proceeds as follows:

The legitime of all legitimate children and descendants collectively is one-half (½) of the hereditary estate (Article 888). This is divided equally among the legitimate children.
Each illegitimate child receives one-half (½) of the share that would pertain to a legitimate child.

Example: An estate of ₱1,000,000 is survived by two legitimate children and two illegitimate children. The collective legitime of the legitimate children is ₱500,000, or ₱250,000 each. Each illegitimate child is entitled to ₱125,000 (one-half of ₱250,000). The total legitime of the children is ₱750,000, leaving the free portion and any surviving spouse’s share to be determined under Articles 892 and 894.

Illegitimate children share in the legitime concurrently with legitimate children, the surviving spouse, and (in default of descendants) legitimate parents or ascendants. Their legitime is taken from the estate before the free portion may be disposed of by will.

V. Rights in Intestate Succession

In intestate succession (Articles 960–1014, Civil Code), the shares are determined by the same proportional rule. Article 983 provides that if legitimate children or descendants and illegitimate children survive, the latter shall be entitled to one-half of the share of each of the former. Thus:

Legitimate children divide the estate such that each receives twice the share of each illegitimate child.
If only illegitimate children survive, they inherit the entire estate in equal shares.
If an illegitimate child concurs with a surviving spouse but no legitimate children, the spouse receives a share equal to that of an illegitimate child (Article 999).
Representation is allowed in the direct descending line, but an illegitimate child may represent only his or her illegitimate parent; representation does not extend upward through a legitimate child to legitimate grandparents unless the line is properly established.

VI. Rights in Testate Succession

A testator may institute an illegitimate child as a voluntary heir for any part of the free portion. However, the legitime cannot be impaired. If the will attempts to reduce or eliminate the legitime, the illegitimate child may file an action for reduction (Article 906) or annulment of the offending dispositions within the prescriptive periods. The illegitimate child may also be disinherited only for causes expressly stated in Article 919 and proved in court.

VII. Legitimation and Its Effects on Inheritance Rights

Articles 177 to 182 of the Family Code provide for legitimation, the process by which an illegitimate child acquires the rights of a legitimate child through the subsequent valid marriage of the parents. Legitimation requires that the parents had no legal impediment to marry at the time of the child’s conception and that the child was conceived before the marriage. Upon legitimation, the child’s rights are retroactive to the time of birth (Article 180), entitling him or her to the full legitime of a legitimate child and eliminating the one-half reduction in intestate shares. Legitimation is recorded in the civil registry and produces full civil status as legitimate for all purposes, including inheritance.

VIII. Prescription and Procedural Aspects

The right to claim filiation and, consequently, inheritance is subject to strict prescription rules under Article 173. For an illegitimate child seeking recognition during the lifetime of the parent, the action must generally be filed while the parent is alive. After the parent’s death, the action may still be pursued by the child or his or her heirs within the periods allowed, provided evidence of filiation is clear and convincing. Failure to establish filiation within the applicable period bars the inheritance claim.

IX. Additional Considerations and Special Situations

Adoption: An adopted child acquires the rights of a legitimate child (Article 189) and is no longer treated as illegitimate for inheritance purposes.
Void Marriages and Good-Faith Children: As noted, Article 54 protects children born before nullity judgments in certain cases.
Concurrence with Other Heirs: The surviving spouse’s legitime under Article 892 is one-eighth (⅛) if there are legitimate children, or one-fourth (¼) if only illegitimate children survive; the spouse concurs with illegitimate children on a one-to-one basis in intestacy when no legitimate descendants exist.
Foreign Elements: Philippine law governs the status of Filipino children regardless of place of birth (nationality principle), subject to the rules on conflict of laws.

The Family Code thus modernized the legal position of illegitimate children by facilitating recognition and equalizing most personal and support rights, while the Civil Code continues to calibrate inheritance shares to preserve the traditional preference for legitimate filiation. These rules ensure that every child with established filiation receives a protected portion of the parent’s estate, reflecting the constitutional mandate to protect the family and the equal protection clause, tempered by the policy of encouraging marriage and legitimate family formation. Philippine courts have consistently upheld these provisions, emphasizing that the rights of illegitimate children, once filiation is proven, are mandatory and cannot be defeated by mere omission in a will or by procedural technicalities where clear evidence exists.