Below is a comprehensive discussion of property inheritance rights for adopted and illegitimate children under Philippine law. This is intended to give an overview of the major legal principles, statutes, and jurisprudence that shape how inheritance is handled for these categories of children in the Philippines.

I. Legal Framework

Civil Code of the Philippines (Republic Act No. 386)
- Governs general provisions on succession (Book III on “Modes of Acquiring Ownership,” Title IV on “Succession”), including rules on legitimes and distribution of estates.
Family Code of the Philippines (Executive Order No. 209, as amended)
- Governs family relations, including the definition of legitimate, illegitimate, and adopted children, as well as parental authority and support.
Domestic Adoption Act of 1998 (Republic Act No. 8552)
- Provides rules on domestic adoption and establishes the status and rights of adopted children, ensuring that adopted children are considered the legitimate children of their adopters.
Other Relevant Laws and Issuances
- RA 9255 (An Act Allowing Illegitimate Children to Use the Father’s Surname)
- Supreme Court decisions clarifying inheritance rights and procedures in establishing filiation.

II. Defining Legitimate, Illegitimate, and Adopted Children

Legitimate Children
- Those conceived or born within a valid marriage.
- They enjoy the full rights of a child under their parents, including full legitime in inheritance.
Illegitimate Children
- Those conceived and born outside of a valid marriage.
- Illegitimate children may be entitled to inherit from their biological parents provided filiation is duly established.
- The law provides that an illegitimate child’s legitime is generally half of that of a legitimate child (see Family Code and Civil Code provisions).
Adopted Children
- Under RA 8552, once adoption is finalized, the adopted child is deemed a legitimate child of the adopter(s) “for all intents and purposes.”
- This includes the right to inherit on the same footing as a legitimate child.

III. Establishing Filiation

Filiation is crucial because the child’s status (legitimate, illegitimate, or adopted) directly impacts inheritance rights. The basic modes of establishing filiation are:

By Birth Certificate
- A validly registered birth certificate naming the parents can be proof of filiation.
By Voluntary Acknowledgment / Recognition
- This can be through an affidavit of acknowledgment or consent contained in a public document, will, or other valid instruments executed by the parent.
By Judicial Action
- In cases of denial or dispute, the child (or a representative) may file a court petition (action for recognition) to establish paternity/maternity through evidence such as DNA tests, testimonial, and documentary proof.
By Adoption Process
- For adopted children, filiation is established through a final adoption decree issued by a court (or by the National Authority for Child Care [NACC], in certain streamlined processes under new regulations). Once the decree is issued, the child becomes the legitimate child of the adopter(s).

IV. Inheritance Rights of Illegitimate Children

Share in the Estate
- The law (Family Code, Civil Code) establishes that the legitime of an illegitimate child is half of the legitime of a legitimate child.
Conditions
- Recognition: An illegitimate child must prove filiation (via birth certificate, recognition, or judicial action).
- Implications if unrecognized: If the child cannot establish filiation, no inheritance rights can be enforced; the child is effectively a stranger to the estate unless the decedent left a will expressly providing for the child.
Legitime vs. Free Portion
- If the deceased left a will, he or she cannot deprive illegitimate children of their legitimes.
- However, there is a free portion of the estate which the testator can distribute as he or she wishes, including potentially increasing an illegitimate child’s share.
Successional Rights in Concurrence with Other Heirs
- The presence of other heirs (e.g., legitimate children, spouse, other illegitimate children) affects the quantum of each share.
- Regardless, an illegitimate child cannot receive more than what the law entitles them to in terms of their legitime unless the decedent specifically grants them more from the free portion of the estate.

V. Inheritance Rights of Adopted Children

Status as a Legitimate Child
- Under the Domestic Adoption Act (RA 8552), once the judgment of adoption becomes final, the adopted child is considered a legitimate child of the adopter(s) for all intents and purposes.
- This legislative intent is to ensure the adopted child is entitled to the same rights as a biological legitimate child, including the right to the legitime.
Effect on Prior Relationships
- Upon adoption, all legal ties between the adoptee and the biological parents (except when the biological parent is the spouse of the adopter or co-adopter in a step-parent or relative adoption) are severed, and new ties are created between the adoptee and the adopter.
- Consequently, the primary inheritance rights are transferred to the adoptive family line. The adopted child will inherit from the adoptive parents as though he/she were their legitimate offspring.
Inheritance from Biological Parents
- As a rule, once adopted, the child’s rights to inherit intestate from the biological parents are extinguished. However, the adoptee may still inherit from the biological parents if named in their will or if the biological parents specifically provide for them in the free portion of their estate.
- The basic principle is that intestate inheritance automatically flows from the legal parents (the adopters) once the adoption decree is final.
Rights and Obligations
- The adoptee owes the same obligations of support, respect, and potential estate claims toward adoptive parents as would a legitimate child.
- Conversely, the adoptive parents have the same rights and obligations (support, parental authority, etc.) as they would have with a biological legitimate child.

VI. Special Notes and Practical Considerations

Illegitimate Child vs. Adopted Child
- Illegitimate Child: Recognized but receives only half the inheritance share of a legitimate child as the legitime.
- Adopted Child: Inherits on equal footing as a legitimate biological child from the adoptive parents.
Testamentary Freedom and Wills
- The testator can distribute the free portion of the estate at will (beyond legitimes).
- If a parent wishes to allocate more to an illegitimate child or to an adopted child (or even reduce the share of a legitimate child), this can be done only within the bounds of the free portion; legitimes must still be respected by law.
Proof and Procedure
- For illegitimate children: Filiation must be demonstrated. The father’s or mother’s recognition in a public document, birth certificate, or successful paternity/maternity action is crucial.
- For adopted children: A final and executory court decree of adoption (or appropriate issuance by the NACC, depending on updated adoption procedures) is necessary to secure the full inheritance rights.
Succession Planning
- Given the complexities and sometimes sensitive nature of illegitimate filiation and adoption, many individuals resort to careful estate planning (via wills, trusts, or prenuptial agreements) to ensure a fair or intended distribution.
Recent Developments
- RA 9255 allows an illegitimate child to use the father’s surname under certain conditions, which can facilitate recognition.
- Courts have shown increasing deference to DNA evidence in establishing paternity.
- Administrative adoption processes (as revised under the Domestic Adoption Act and further streamlined by subsequent regulations) aim to make adoption swifter, ensuring that the adopted child’s rights are established without delay.

VII. Summary of Key Points

Illegitimate children
- Entitled to a legitime equal to half of the share of a legitimate child.
- Must establish filiation through birth certificate, acknowledgment, or judicial proceeding.
- May inherit more if so provided in the free portion of a will.
Adopted children
- Treated in law as legitimate children of their adoptive parents.
- Inherit in the same manner and share as legitimate biological children.
- Lose intestate inheritance rights from biological parents (except in certain step-parent adoptions or if specifically named in a will by the biological parents).
Proof and Documentation
- Proper documentation (court decrees, civil registry records) is key to ensuring inheritance claims can be enforced.
Hierarchy and Conflict
- In cases with multiple heirs (legitimate, illegitimate, adopted, surviving spouse), the estate is distributed according to the established rules of concurrence of heirs, with each category receiving its mandated legitime.
- Where a will exists, the testator must respect the reserved legitimes but may distribute the free portion as desired.
Importance of Legal Counsel
- Parties dealing with inheritance involving illegitimate and/or adopted children are strongly advised to consult legal professionals for accurate estate planning and to avoid protracted litigation.

Conclusion

In the Philippine legal setting, the distinction between legitimate, illegitimate, and adopted children significantly affects their respective inheritance rights. Illegitimate children have a guaranteed (though reduced) share compared to legitimate offspring, provided that their filiation is legally recognized. Adopted children, once formally adopted, enjoy all the rights (including inheritance rights) of legitimate children. These rules underscore the importance of proper legal processes—either for establishing filiation or finalizing an adoption—and highlight the protective philosophy of Philippine law to ensure that children, regardless of their circumstances, have recognized rights to their parents’ estates (albeit with differing entitlements).

As rules on family law and inheritance can be quite technical and are prone to amendments or clarifications by the courts, individuals dealing with these matters are strongly encouraged to seek the guidance of licensed legal practitioners, especially when drawing up wills, executing adoptions, or asserting inheritance claims.