Short answer. The law groups relatives into a direct line — ascendants and descendants, like parent to child — or a collateral line, people who are not ascendants or descendants of each other but share a common ancestor, like siblings or cousins. Each line is made of a series of degrees, which is how closeness is measured.
What the law says
A series of degrees forms a line, which may be either direct or collateral.
Civil Code, Article 964 — Lines of Relationship. Read the full provision →
The line comes before the degree
Article 964 starts from the idea that a series of degrees forms a line. Before counting how many degrees separate two relatives, the law first asks what kind of line connects them — because a direct line and a collateral line are counted differently. Getting the line right is the first step in working out any relationship for inheritance purposes; get the line wrong, and the degree count that follows will be wrong too, since the two lines are not interchangeable ways of describing the same relationship.
The direct line: parents, children, and beyond
A direct line is, in the article's words, "that constituted by the series of degrees among ascendants and descendants." This covers a person and their parents, grandparents, and further back on one side, or their children, grandchildren, and further forward on the other. It is a straight line of descent in one direction or the other — no relative in a direct line stands to one side of the other; each generation proceeds directly from, or directly into, the next.
The collateral line: relatives who share an ancestor
A collateral line is defined by contrast: it is "constituted by the series of degrees among persons who are not ascendants and descendants, but who come from a common ancestor." Siblings are the clearest example — neither is the ascendant or descendant of the other, but both descend from the same parents. Cousins, aunts, uncles, nephews, and nieces are also collateral relatives under this same test: what connects them is a shared ancestor somewhere up the line, not a direct descent from one to the other.
Why the distinction matters for an estate
Which line a relative belongs to affects how the law treats their claim to an estate, because succession rules are built around these two categories rather than around relationship labels alone. A family sorting out who inherits from whom should first place each relative correctly — direct or collateral — since that classification, and not just the everyday name for the relationship, is what the rest of the succession rules build on.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Maria Mendoza, et al. vs. Julia Policarpio, et al, G.R. No. 176422, March 20, 2013 — read the decision on LawPhil →