Can an illegitimate child use the father's surname, and what are their inheritance rights?

Why

Article 176 of the Family Code of the Philippines originally mandated that all illegitimate children must use the surname of their mother. Republic Act No. 9255 amended this provision so that illegitimate children may use the father's surname if the father has expressly recognized his filiation. The father keeps the right to sue in court during his lifetime to prove non-filiation.

Under RA 9255, the recognition must appear in one of three forms: (1) the record of birth in the civil register, such as the father's acknowledgment in the Certificate of Live Birth; (2) an admission in a public document, such as a notarized Affidavit of Admission of Paternity (AAP); or (3) an admission in a private handwritten instrument made by the father. Without this express acknowledgment, the child must continue bearing the mother's surname.

Even when an illegitimate child bears the father's surname, sole parental authority and legal custody remain exclusively with the mother under Article 176. The Supreme Court has applied this rule in cases such as Briones v. Miguel (G.R. No. 156343, October 18, 2004) and Masbate v. Relucio (G.R. No. 235498, July 30, 2018): the father remains obliged to give support and may be granted visitation rights according to the child's best interests, but the mother will not be deprived of custody absent compelling reasons, such as proof of her unfitness.

Under Article 887 of the Civil Code, an illegitimate child is a compulsory heir of the parent whose filiation is established. Under Article 176 of the Family Code, the legitime (the portion of an estate reserved by law that cannot be given away) of each illegitimate child is one-half (50%) of the legitime of a legitimate child. Under Article 895 of the Civil Code, illegitimate children's legitimes are taken from the free portion of the estate and cannot exceed it, so where there are many heirs the actual amount can be smaller.

Under Article 992 of the Civil Code, known as the 'Iron Curtain Rule', an illegitimate child cannot inherit by intestate succession from the legitimate children and relatives of their father or mother, nor can those legitimate relatives inherit from the illegitimate child in the same manner. In Aquino v. Aquino (G.R. No. 208912, December 7, 2021), however, the Supreme Court held that this bar applies only between collateral relatives, such as half-siblings, aunts, and uncles, and that a child whose parents did not marry may inherit from a grandparent by right of representation.