Below is a general discussion of the legal rights of a child from a previous marriage, where the child has not been legally adopted by the new spouse of their biological parent, under Philippine law. This overview is based on the Family Code of the Philippines (Executive Order No. 209, as amended), relevant provisions of the Civil Code, and other pertinent laws such as the Child and Youth Welfare Code (Presidential Decree No. 603). For specific legal advice, it is always best to consult a qualified Filipino attorney, as individual circumstances can vary greatly.

1. Status of the Child

Legitimate vs. Illegitimate Status
- A child from a valid previous marriage is considered a legitimate child of his or her biological parents.
- Legitimacy entitles the child to a host of rights under Philippine law, including the right to bear the surname of the father (if desired and in accordance with law), the right to support from both biological parents, and the right to inherit from them.
- If the child was born out of wedlock (i.e., parents were not married to each other), the child is an illegitimate child. However, the child’s status—legitimate or illegitimate—remains in relation to the biological parents, not to the step-parent or new spouse, unless adoption takes place.
Effect of Non-Adoption by the Stepparent
- Without legal adoption, the child does not acquire the same rights with respect to the step-parent that a legally adopted child would acquire.
- The non-adopted child retains all the rights that flow from their biological parent-child relationship (vis-à-vis the biological parents), but no automatic legal rights arise between the step-parent and the child unless provided by specific legal or contractual arrangements (e.g., naming the child as a beneficiary in life insurance).

2. Parental Authority and Custody

Parental Authority
- Under the Family Code, parental authority belongs to the child’s biological parents.
- The step-parent does not automatically have parental authority over a child from a previous marriage unless:
  1. The biological parent and step-parent jointly exercise it because they are the de facto guardians in the same household, and
  2. The biological parent delegates or shares day-to-day responsibilities with the step-parent.
- However, this sharing of responsibilities is more of an arrangement in fact rather than a legal delegation that grants the step-parent full parental authority.
Custody
- Custody typically goes to the biological parent (the father or mother) as a matter of law.
- If the biological parent who has custody passes away or becomes incapacitated, parental authority usually shifts to the other biological parent (if still living and capable).
- If both biological parents are deceased or judicially declared unfit, a court-appointed guardian (which could be a step-parent, if the court finds this to be in the child’s best interest) may assume custody.

3. Support Obligations

Support from the Biological Parent
- Both biological parents are legally obliged to provide support to their child (Family Code, Articles 194–200).
- Support includes everything indispensable for sustenance, dwelling, clothing, medical needs, education, and transportation.
- The new spouse (step-parent) is generally not legally bound to support the child unless:
  1. The step-parent has legally adopted the child, thereby assuming all obligations of a parent, or
  2. There is a specific agreement or commitment to provide support.
Use of Conjugal or Community Property
- Even though the step-parent is not personally obliged to support the child, the biological parent may use the conjugal property (if the new marriage is under the conjugal partnership of gains) or the absolute community property (if the new marriage is under the absolute community regime) to fulfill support obligations to the child, provided that such support is consistent with the property regime’s rules.
- This can sometimes create friction or confusion about the division of resources, but the law recognizes that the biological parent’s duty to support takes precedence.

4. Inheritance and Succession

Right to Inherit from the Biological Parent
- A child from a previous marriage—whether legitimate or illegitimate—remains a compulsory heir of the biological parent.
- This means the child has a reserved portion (the legitime) from the parent’s estate under the Civil Code. No subsequent marriage or birth of half-siblings can entirely disinherit a compulsory heir unless grounds for disinheritance exist (which are strictly interpreted under the law).
Right to Inherit from the Step-Parent
- No automatic right to inherit exists between the step-parent and the step-child if no legal adoption occurred. The step-parent can choose to name the child as an heir via a will (testamentary disposition), but absent such a will or adoption, the child has no compulsory heir status with respect to the step-parent.
- If the step-parent wishes the child to inherit, an alternative is to execute a last will and testament naming the child as a beneficiary, or to adopt the child legally so the child becomes a compulsory heir.

5. Use of Surnames

Surname of the Child
- A legitimate child customarily uses the surname of the father (under existing Philippine laws and Supreme Court rulings).
- If the biological parents are not married, the child may use the mother’s surname or the father’s surname if acknowledged under the rules of RA 9255 (The “Revilla” Law).
- No mandatory change of surname to the step-parent’s name is possible if there is no adoption. The child typically retains their biological father’s or mother’s surname, depending on legitimacy and acknowledgment.
Possible Change of Surname
- Formal change of surname (to that of the step-parent) would require either:
  1. Legal adoption, or
  2. A court-approved change of name under Rule 103 of the Rules of Court, which requires showing compelling reasons.

6. Other Rights and Considerations

Government Benefits
- The child’s primary access to benefits—such as SSS (Social Security System) or GSIS (Government Service Insurance System) survivor’s benefits—derives from the biological parent.
- The step-parent has no automatic obligation to list the child as a beneficiary in private or government insurance, unless the step-parent voluntarily does so or legally adopts the child.
Education and Healthcare Decisions
- The biological parent(s) have the right and duty to make decisions about the child’s education and healthcare.
- The step-parent may be involved in day-to-day care or minor medical decisions if the child resides with them, but major decisions typically require the consent of the biological parent.
Possible De Facto Guardian Role
- If the child primarily resides with the biological parent and the step-parent, the step-parent often assumes a de facto guardian role.
- While this grants the step-parent practical responsibilities, it does not automatically create the same legal rights or obligations as a biological or adoptive parent.
Legal Adoption as the Standard for Full Rights
- Should the biological parent and step-parent wish the child to enjoy full parental rights and the same inheritance rights in relation to the step-parent, legal adoption under Republic Act No. 8552 (Domestic Adoption Act) is the process to follow. Adoption would:
  - Bestow upon the step-parent the full parental authority over the child.
  - Make the child a compulsory heir to the step-parent.
  - Entitle the child to the step-parent’s surname and any attendant benefits (e.g., intestate succession rights).

7. Summary of Key Points

Parental Authority & Custody: Remains with the biological parent. The step-parent has no automatic legal authority unless they adopt or obtain guardianship.
Support: Only the child’s biological parents are primarily responsible unless there is a legal adoption or specific agreement.
Inheritance:
- The child remains a compulsory heir of their biological parent, regardless of any subsequent marriages.
- The child does not inherit from the step-parent unless legally adopted or specifically named in a will.
Name and Surname: The child retains the surname in accordance with the rules on legitimate or illegitimate children. A step-parent’s surname can only be used if there is a legal adoption or a court-approved name change.
Government and Other Benefits: The child relies on the biological parent’s entitlements. Step-parents are not obligated to list the child as a beneficiary unless they wish to or they adopt the child.
Legal Remedies: If the child’s rights (to support, inheritance from the biological parent, etc.) are violated, the child or the child’s guardian may seek legal remedies in court.

8. Practical Tips and Considerations

Open Communication: If a step-parent and biological parent plan for the child to be fully integrated into the new family setup, explore legal adoption or a clear, written agreement on financial support.
Estate Planning: For the step-parent who wants to provide for the child even without adoption, a last will and testament or beneficiary designations can ensure the child receives benefits or assets.
Documentation: Keep records of expenses for the child, particularly if issues regarding support or inheritance rights may arise.
Court Guidance: In cases of dispute—e.g., over custody or support—seek clarification or intervention from the court to protect the child’s rights.

Important Laws and References

Family Code of the Philippines (E.O. No. 209, as amended) – Governs marriage, parental authority, and support obligations.
Civil Code of the Philippines – Covers successional rights, property regimes, and basic family law principles not repealed by the Family Code.
Presidential Decree No. 603 (Child and Youth Welfare Code) – Addresses the welfare of children, including parental authority and guardianship.
Republic Act No. 8552 (Domestic Adoption Act) – Lays out procedures and effects of domestic adoption in the Philippines.
Republic Act No. 9255 (Revilla Law) – Governs the use of the father’s surname by illegitimate children when acknowledged by the father.

Conclusion

A child from a previous marriage who is not adopted by the new spouse retains all rights against their biological parents under Philippine law, including the right to support and inheritance from those parents. However, no automatic legal rights—such as inheritance, support, or use of surname—flow from the step-parent to the child unless there is legal adoption or a specific agreement/will. Understanding these distinctions helps families navigate financial responsibilities, estate planning, and day-to-day decision-making for the child’s welfare. When in doubt, consulting a family law attorney in the Philippines is advisable to address unique circumstances and ensure the child’s best interests are protected.