Short answer. Article 899 of the Civil Code gives the surviving spouse one-eighth of the estate and the illegitimate children one-fourth, both taken from the free portion, leaving one-eighth freely disposable. The legitimate parents take the remaining half as their own legitime as ascendants.
What the law says
When the widow or widower survives with legitimate parents or ascendants and with illegitimate children, such surviving spouse shall be entitled to one-eighth of the hereditary estate of the deceased which must be taken from the free portion, and the illegitimate children shall be entitled to one-fourth of the estate which shall be taken also from the disposable portion. The testator may freely dispose of the remaining one-eighth of the estate.
Civil Code, Article 899 — Spouse, Ascendants and Illegitimate Children. Read the full provision →
The arithmetic of the combination
Article 899 governs one specific line-up of heirs: a surviving spouse, legitimate parents or other ascendants, and illegitimate children, with no legitimate children. Under the Civil Code's scheme the legitimate parents take one-half of the estate as their legitime as ascendants. The article then allocates what remains. The spouse receives one-eighth, and the illegitimate children collectively receive one-fourth, both carved out of the free portion. The last sentence states what is left: the testator may freely dispose of the remaining one-eighth. Where there is more than one illegitimate child, the one-fourth is divided equally among them, not multiplied.
How this article reads today
The share above was computed on the classification of children used when the Civil Code took effect in 1950, and it must now be read subject to the Family Code. The Family Code provides that the legitime of each illegitimate child is one-half of the legitime of a legitimate child, and that except for this modification all other provisions of the Civil Code governing successional rights remain in force. It also recognises a single class of illegitimate child, so the Civil Code's older sub-classifications — the distinctions between natural and other illegitimate children — no longer apply. Anyone dividing an estate on the strength of an old Civil Code annotation should check it against that rule.
Where the free portion actually goes
Note the structure of the article: the spouse's eighth and the children's fourth are described as taken from the free portion, which is why only one-eighth is left as truly disposable. If the deceased left no will, that final eighth does not simply vanish — the rules on intestate succession distribute it, and the practical result can differ from the testamentary picture. If there is a will, that eighth is what the testator could give to anyone he liked: a friend, a charity, or any of these same heirs by way of an additional legacy on top of their legitimes.
Before you divide anything
The fractions apply to the net hereditary estate, not to the family's assets as a whole. If the deceased was married under absolute community or conjugal partnership, the regime is liquidated first and the surviving wife's own share of that property is hers already, outside the estate. Debts, funeral and administration expenses come off before the fractions are applied. Filiation also has to be established: an illegitimate child's right depends on proof of recognition or of filiation, and disputes here are common. Because a single additional heir — a legitimate child, another illegitimate child — moves every fraction, list the whole family first and compute afterwards.