Article 187Family Code, Art. 187

The following may not be adopted:(1) A person of legal age, unless he or she is a child by nature of the adopter or his or her spouse, or, prior to the adoption, said person has been consistently considered and treated by the adopter as his or her own child during minority. (2) An alien with whose government the Republic of the Philippines has no diplomatic relations; and (3) A person who has already been adopted unless such adoption has been previously revoked or rescinded. (30a, EO 91 and PD 603)