Short answer. One-third of the estate. Article 894 gives the surviving spouse one-third and the illegitimate children another third to share between them, leaving the remaining third at the testator's free disposal. A bequest larger than that third is not void, but it is cut back to fit.
What the law says
If the testator leaves illegitimate children, the surviving spouse shall be entitled to one-third of the hereditary estate of the deceased and the illegitimate children to another third. The remaining third shall be at the free disposal of the testator.
Civil Code, Article 894 — Spouse and Illegitimate Children. Read the full provision →
What the law says
In all cases of illegitimate children, their filiation must be duly proved.
Civil Code, Article 887 — Who the Compulsory Heirs Are. Read the full provision →
Thirds, and how they are shared
The article divides the estate in three: if the testator leaves illegitimate children, the surviving spouse shall be entitled to one-third of the hereditary estate of the deceased and the illegitimate children to another third. The remaining third shall be at the free disposal of the testator. Note that the children's third is a collective share, divided among them however many there are. Two illegitimate children take a sixth each, four take a twelfth each. The spouse's third does not move with their number, and neither does the free portion.
This is a better position than it looks
Illegitimate children are compulsory heirs, and where no legitimate children compete with them the share reserved to them is substantial. It is worth being precise about the comparison, though: where legitimate children do survive, illegitimate children's legitimes are computed by reference to a legitimate child's share and are drawn from the free portion, which is a materially different exercise. The generous third in this article is a consequence of there being no legitimate descendants at all, and it disappears the moment one appears.
Filiation has to be proved, and proved with documents
None of the arithmetic starts until the relationship is established. The Code is blunt about it — in all cases of illegitimate children, their filiation must be duly proved — and it is the point on which these estates are most often fought, usually by relatives with an interest in the third going elsewhere. The record of birth, an acknowledgment signed by the father, an admission in a public or private document, or another admissible proof does the work. Collect it while the people who can attest to it are still available.
What the free third really buys
Only a third of the net estate is available for a legacy to anyone outside those two classes, and it is a third of the estate after the marital property regime is liquidated and debts, taxes and expenses are paid. A will that gives more is not void; the excess is reduced on the heirs' petition insofar as it impairs their legitimes. If the intention is to leave something to a sibling, a parent or a partner, size the gift against that third — and put it in a valid will, because intestacy will not produce it.
What the Family Code changed about this
One part of the article above no longer states current law. The fractions it reserves to legitimate children and to the surviving spouse still stand, but the shares were worked out on the classification of children in use when the Civil Code took effect in 1950. The Family Code now fixes the legitime of each illegitimate child at one-half of the legitime of a legitimate child, and provides that apart from that modification the Civil Code's rules on successional rights remain in force. So read the article for the structure and the Family Code for an illegitimate child's share.
Related provisions
- Civil Code, Article 894 — Spouse and Illegitimate Children
- Civil Code, Article 887 — Who the Compulsory Heirs Are
- Civil Code, Article 907 — Reduction Of Inofficious Dispositions