Short answer. Philippine law allows several categories to be adopted: a child under 18 declared available for adoption, a spouse's legitimate child, an illegitimate child, an adult long treated as one's own child since minority, and others. Note that adoption is now an administrative process under Republic Act 11642 (2022).
What the law says
The following may be adopted: (a) Any person below eighteen (18) years of age who has been administratively or judicially declared available for adoption; (b) The legitimate son/daughter of one spouse by the other spouse; (c) An illegitimate son/daughter by a qualified adopter to improve his/her status to that of legitimacy
RA 8552, Section 8 — Who May Be Adopted. Read the full provision →
The law that governs today
Before listing who may be adopted, one point is essential. Adoption in the Philippines is now an administrative process. Republic Act 11642 (2022), the Domestic Administrative Adoption and Alternative Child Care Act, moved adoption out of the courts and to the National Authority for Child Care (NACC), and it restated the qualifications and the consent and eligibility rules. The categories of who may be adopted, drawn from the earlier law, Republic Act 8552, remain a useful guide, but the procedure and the qualifying conditions are today governed by RA 11642. So read the list below as the substance, while remembering the process runs through the NACC, not a court.
Who may be adopted: the core cases
Republic Act 8552 lists who may be adopted, and the list remains a helpful map of the categories. It provides that the following may be adopted: (a) Any person below eighteen (18) years of age who has been administratively or judicially declared available for adoption; (b) The legitimate son/daughter of one spouse by the other spouse; (c) An illegitimate son/daughter by a qualified adopter to improve his/her status to that of legitimacy. So the classic case is a minor declared available for adoption, but the law also expressly allows a stepparent to adopt a spouse's legitimate child, and a qualified adopter to adopt an illegitimate child to lift that child to the status of legitimacy.
Adults and other special cases
Adoption is not limited to young children. The list continues: (d) A person of legal age if, prior to the adoption, said person has been consistently considered and treated by the adopter(s) as his/her own child since minority. So an adult who was raised as one's own child since minority may still be adopted. It also includes (e) A child whose adoption has been previously rescinded, and (f) A child whose biological or adoptive parent(s) has died, but with an important safeguard: no proceedings shall be initiated within six (6) months from the time of death of said parent(s). That waiting period guards against rushing a child into adoption during the immediate grief after a parent's death.
What adoption achieves, and its limits
Whatever the category, the lasting effects of a completed adoption are significant and survive the change in procedure. The adopted child is treated as the legitimate child of the adopter, and the two gain reciprocal rights, including succession, so the child may inherit from the adopter and the adopter from the child. What this provision does not do is set the qualifications of the adopter or the detailed steps; those are found elsewhere and are now handled administratively under RA 11642. Anyone considering adoption should therefore approach the National Authority for Child Care and check the current requirements, using this list to see whether the person to be adopted fits a recognized category.