Under Philippine law, specifically under Republic Act No. 9255, illegitimate children possess particular rights, especially regarding their relationships with and entitlements from their biological parents. Here’s a meticulous breakdown of the law as it applies to paternity and filiation, specifically in relation to illegitimate children and their rights:

1. Background of R.A. No. 9255

Republic Act No. 9255 was enacted to amend Article 176 of the Family Code of the Philippines. Before R.A. No. 9255, an illegitimate child could only use the surname of their mother, thus creating a distinction between legitimate and illegitimate children based on surname usage. This amendment, signed into law on February 24, 2004, allows illegitimate children to use the surname of their biological father under specific conditions.

2. Key Provisions of R.A. No. 9255 on the Rights of Illegitimate Children

a. Right to Use the Father’s Surname

Article 176, as Amended by R.A. No. 9255: Under this law, an illegitimate child can now use the surname of the father if he/she is expressly recognized by the father.
Conditions for the Use of the Father’s Surname: The father must acknowledge the child through a public document (such as an affidavit of acknowledgment or recognition) or a private handwritten instrument that the father personally signed.

b. Legal Procedure for Registering the Father’s Surname

If the father acknowledges the child after the child’s birth has been registered, the change of the child’s surname must follow the process established by the Office of the Civil Registrar-General under the Implementing Rules and Regulations (IRR) of R.A. No. 9255.
Administrative Requirements: The child’s birth certificate must be annotated to reflect the change of surname, and supporting documents such as the father’s affidavit of acknowledgment are required.

c. Parental Authority

Parental Authority over Illegitimate Children: In accordance with Article 176, even if an illegitimate child uses the father’s surname, the mother remains the sole authority over the child. She has full custodial rights unless the court decides otherwise.
Exceptions: If the child’s welfare is at risk, the court may award custody to the father or another suitable guardian.

d. Support Obligations

Right to Support: Illegitimate children are entitled to financial support from their biological father, in line with Articles 195 and 196 of the Family Code. This includes essential needs such as food, shelter, clothing, and medical care, based on the father’s financial capacity.
Legal Remedy: Should the father neglect his duty to support the child, the mother or legal guardian may file a case for child support to compel compliance.
Equity of Support: Although legitimate children may be given preference in support, illegitimate children are legally entitled to a fair portion of support.

3. Inheritance Rights of Illegitimate Children

Illegitimate children are recognized as compulsory heirs under the Civil Code, and they have the right to inherit from their biological parents, although their share is generally less than that of legitimate children.

One-Half Share of a Legitimate Child’s Inheritance: An illegitimate child is entitled to one-half of what a legitimate child would inherit.
No Right to Inherit from the Father’s Family: Illegitimate children do not have inheritance rights over the father’s legitimate family members, unless otherwise provided for in a will.

4. Birth Certificate Annotation and Legal Documentation Requirements

a. Annotation of the Birth Certificate

Original Registration Requirements: When an illegitimate child is registered at birth, the child’s surname generally defaults to the mother’s. Should the father later recognize the child, the Civil Registrar must annotate the birth certificate to reflect the father’s surname.
Court Involvement Not Required: This procedure is administrative in nature and does not require a court order if all documents are complete and valid.

b. Implementation Rules and Regulations (IRR) of R.A. No. 9255

Compliance with IRR: The rules require that the process be completed through affidavits and documented acknowledgment forms to ensure clarity and reduce any procedural delays or disputes.

5. Additional Rights of Illegitimate Children

a. Rights to Identity and Name

Recognition of Family Ties: Even if classified as “illegitimate,” children have the right to be acknowledged as offspring of their biological father, affecting their psychological and social well-being.

b. Non-Discrimination Clause

Right Against Discrimination: Although there are differences in terms of parental authority and inheritance, illegitimate children are afforded protection against discrimination under various Philippine laws, including the Anti-Child Abuse Act.

c. Civil Status and Social Recognition

The law recognizes the unique civil status of illegitimate children, and amendments like R.A. No. 9255 help align with modern views, aiming to lessen the stigma associated with illegitimacy.

6. Challenges in Implementation and Legal Recourse

a. Legal Recourse for Recognition

Judicial Declaration: If a father refuses to recognize his illegitimate child, the child (or the mother on the child’s behalf) may seek a judicial declaration of paternity through a paternity case, which may involve evidence such as DNA testing.

b. Enforcement of Support and Inheritance Rights

Filing for Support: Mothers of illegitimate children can file for child support through a court action if the father fails to voluntarily provide.
Inheritance Disputes: In case of inheritance disputes, illegitimate children may file a claim as compulsory heirs to receive their rightful share under the Civil Code.

7. Summary of Practical Applications

Acknowledgment Requirement: Fathers must formally acknowledge their illegitimate children through a written, notarized document or public acknowledgment.
Support and Inheritance Rights: Despite the classification, illegitimate children have enforceable rights to support and inheritance.
Procedure for Using the Father’s Surname: Administrative process through the Civil Registrar, not requiring a court order if documentation is compliant.

R.A. No. 9255 was a significant step in protecting the rights of illegitimate children by recognizing their social identity and legal rights while balancing parental obligations. It highlights the progression towards inclusivity and recognition of all children’s rights in Philippine society.