Short answer. The relationship between the killer and the victim, and nothing else. If the person killed was the offender's father, mother, child, another ascendant or descendant, or his spouse, the crime is parricide however the killing was carried out. Manner and motive decide murder; blood or marriage decides parricide.
What the law says
Any person who shall kill his father, mother, or child, whether legitimate or illegitimate, or any of his ascendants or descendants, or his spouse, shall be guilty of parricide
Revised Penal Code, Article 246 — Parricide: Killing A Relative. Read the full provision →
Exactly who is covered
Article 246 of the Revised Penal Code names them precisely: father, mother, or child, whether legitimate or illegitimate; any other ascendant or descendant; and the spouse. Grandparents and grandchildren are inside it because they are ascendants and descendants. What falls outside is just as important. Brothers and sisters are not covered. Uncles, aunts, nephews and cousins are not. Parents-in-law and children-in-law are not, because affinity is not the relationship the article describes. Adoptive relationships are not blood relationships either. A killing of any of those people is homicide or murder, with the relationship treated as an aggravating circumstance rather than as the definition of the crime.
Two limits the text quietly imposes
The extension to ascendants and descendants is confined to legitimate relations — only the father, mother and child are expressly covered whether legitimate or illegitimate. And the spouse must be a lawful spouse: a live-in partner, however long the relationship, is not a spouse, so killing a partner is not parricide. That makes the validity of the marriage a live issue in these cases, and the marriage must be proved, ordinarily by the marriage certificate rather than by the parties' say-so. There is one age-based exception at the other end: a child less than three days old falls under the article on infanticide instead.
The offender must know the relationship
Parricide requires that the accused knew who he was killing. A person who shoots at a stranger in the dark and turns out to have killed his own father has committed a killing, but not this one — the special gravity of the offence rests on the deliberate violation of the family tie. The prosecution therefore has to establish both the relationship and the accused's awareness of it, and the information must allege the relationship. Where it does not, a conviction for parricide cannot stand even if the relationship is proved at trial, because the accused was never charged with what makes the crime what it is.
The penalty today
The article states the penalty as reclusion perpetua to death. That must be read subject to Republic Act No. 9346 (2006), which prohibits the imposition of the death penalty in the Philippines; where the Revised Penal Code's nomenclature is used, reclusion perpetua is imposed in its place. So parricide today carries reclusion perpetua, without eligibility for parole under the terms of that statute. Killings of a spouse frequently arise against a background of domestic abuse, and the special law on violence against women and their children may bear on the same facts. No outcome can be promised. This page is general legal information, not advice; to have a case reviewed, you can book a consultation.