Introduction

Intestate succession, governed primarily by the Civil Code of the Philippines (Republic Act No. 386, as amended), occurs when a person dies without a valid will, leaving the distribution of their estate to statutory rules. These rules prioritize compulsory heirs and aim to reflect familial obligations while ensuring equitable sharing among qualified relatives. The focus here is on the shares allocated to legitimate children, the surviving spouse, and half-siblings in various scenarios. Legitimate children are those born or conceived within a valid marriage or subsequently legitimated. The surviving spouse is the legally married partner at the time of death. Half-siblings, or siblings of the half-blood, share only one common parent with the decedent.

The estate subject to intestate succession includes all property owned by the decedent at death, minus debts, funeral expenses, and administrative costs. Distribution follows principles of representation (where descendants stand in place of predeceased heirs), concurrence (where multiple classes of heirs share), and exclusion (where closer heirs bar remoter ones). Key provisions are found in Articles 960 to 1014 of the Civil Code, supplemented by jurisprudence from the Supreme Court of the Philippines.

Fundamental Principles of Intestate Succession

Before delving into specific shares, it is essential to understand the order of intestate heirs under Article 962:

Legitimate children and descendants.
Legitimate parents and ascendants.
Illegitimate children and descendants.
Surviving spouse.
Brothers, sisters, nephews, and nieces (collateral relatives within the fourth degree).
Other collateral relatives within the fifth degree.
The State (escheat).

Heirs in a prior order exclude those in subsequent orders, except where concurrence is provided. For instance, the surviving spouse concurs with classes 1, 2, and 3 but excludes classes 5 and beyond. Representation applies per stirpes (by branch) for descendants but not for ascendants or collaterals, except for nephews and nieces representing siblings.

The legitime— the reserved portion for compulsory heirs—underlies intestate distribution. Legitimate children's legitime is one-half of the estate, divided equally. The surviving spouse's legitime varies: one-fourth when concurring with legitimate children, or one-third with illegitimate children. However, in pure intestacy, shares are computed to satisfy these reservations while distributing the remainder.

Shares of Legitimate Children

Legitimate children are primary compulsory heirs and inherit first in intestacy. Their shares depend on concurring heirs.

When Legitimate Children Inherit Alone

If the decedent leaves only legitimate children (no surviving spouse, ascendants, or other heirs), the entire estate is divided equally among them (Article 980). Representation applies: if a child predeceases the decedent, their descendants inherit per stirpes. For example, if the decedent has three legitimate children, but one is deceased with two children, the estate is divided into three parts—one-third to each living child, and one-third split equally between the grandchildren.

Adopted children, under Republic Act No. 8552 (Domestic Adoption Act), are treated as legitimate for succession purposes and share equally.

Concurrence with Surviving Spouse

When legitimate children and the surviving spouse concur (no illegitimate children or ascendants claiming), the estate is divided into equal parts corresponding to the number of legitimate children plus one for the spouse (Article 996). Each child receives one part, and the spouse receives one part equivalent to a child's share. This satisfies the children's collective legitime of one-half and allocates the free portion.

Example: Decedent with two legitimate children and a surviving spouse. The estate is divided into three equal parts—one to each child, one to the spouse. If one child is predeceased with descendants, representation maintains the branch's share.

If there are also illegitimate children, shares adjust: legitimate children receive twice the share of illegitimate ones (Article 983), with the spouse's share equal to a legitimate child's. The formula becomes: divide the estate into parts where each legitimate child gets 2 units, each illegitimate gets 1 unit, and the spouse gets 2 units (equivalent to a legitimate child).

Concurrence with Illegitimate Children (Without Spouse)

If only legitimate and illegitimate children, the estate is divided with legitimate children getting shares twice those of illegitimate children (Article 983). Total parts = (2 × number of legitimate) + (1 × number of illegitimate).

Other Considerations

Predeceased or Unworthy Children: Shares go to descendants via representation. Unworthiness (e.g., due to attempts on the parent's life under Article 1032) disqualifies but may transmit to descendants.
Legitimation: Children legitimated after birth (e.g., via subsequent marriage under Article 178) inherit as legitimate.
Jurisprudence: Cases like Heirs of Ureta v. Heirs of Ureta (G.R. No. 165748, 2011) emphasize equal division among legitimate children, barring disinheritance which requires a will.

Shares of the Surviving Spouse

The surviving spouse inherits in concurrence or exclusion, but never as a sole heir unless all prior classes are absent.

Concurrence with Legitimate Children

As noted, the spouse receives a share equal to one legitimate child (Article 996). This is computed after satisfying the children's legitime. If the estate is insufficient, reductions are pro-rata.

If illegitimate children also concur, the spouse's share remains equal to a legitimate child's (twice an illegitimate's).

Concurrence with Ascendants

If no descendants or illegitimate children, the spouse shares with legitimate parents or ascendants (Article 993). The estate is divided equally: one-half to the ascendants (divided per line if both paternal and maternal), one-half to the spouse.

Example: Decedent with surviving spouse and parents. Parents share one-half equally (or per line if grandparents), spouse gets one-half.

Concurrence with Illegitimate Children (Without Descendants or Ascendants)

The spouse and illegitimate children divide the estate equally (Article 994), with representation for illegitimate descendants.

When the Spouse Inherits Alone

In the absence of descendants, ascendants, and illegitimate children, the spouse inherits the entire estate (Article 995). This excludes siblings and other collaterals.

Special Rules

Common-Law Spouses: Not recognized; only legal spouses qualify. Bigamous marriages void the second spouse's rights.
Separation: Legal separation does not disqualify unless the spouse is guilty (Article 63, Family Code).
Community Property: The spouse's share in conjugal or absolute community property is settled first, separate from intestate succession.
Jurisprudence: Vitug v. Court of Appeals (G.R. No. 82027, 1990) clarifies the spouse's concurrence rights, emphasizing protection against disinheritance in wills but automatic in intestacy.

Shares of Half-Siblings

Half-siblings inherit as collateral relatives only in the absence of all prior heirs: no descendants, no ascendants, no illegitimate children, and no surviving spouse (Article 1003). They share with full-blood siblings, nephews, and nieces.

Order and Exclusion

Collaterals inherit in the fifth order, limited to the fourth civil degree (siblings, nephews/nieces). Half-siblings are included but receive half the share of full-blood siblings (Article 1006).

If the decedent leaves full-blood and half-blood siblings, the estate is divided where full-blood get two shares for each one share of half-blood.

Example: Decedent with two full-blood siblings and one half-blood sibling. Total parts = (2 × 2) + 1 = 5. Each full-blood gets 2/5, half-blood gets 1/5.

Representation in Collaterals

Nephews and nieces represent predeceased siblings (Article 1005), inheriting per stirpes. Half-blood relations apply: a half-blood nephew gets half the share of a full-blood one if representing the same line.

If only nephews and nieces (no surviving siblings), they inherit per capita if all of the same degree, or per stirpes if mixed.

Concurrence and Preferences

Full-Blood vs. Half-Blood: Full-blood preferred in shares, but half-blood exclude remoter collaterals (e.g., cousins).
Adopted Siblings: Adoption creates full-blood equivalence for succession.
No Concurrence with Spouse: The spouse's presence excludes all collaterals, including half-siblings.
Jurisprudence: In re: Intestate Estate of Cristina Aguinaldo-Suntay (G.R. No. 183053, 2010) discusses collateral succession, affirming the half-blood rule and representation limits.

Specific Scenarios Involving All Parties

While legitimate children, spouse, and half-siblings rarely concur (as children exclude collaterals), hypothetical combinations arise if classifications overlap (e.g., half-siblings as illegitimate children).

If Half-Siblings Are Illegitimate

Illegitimate half-siblings inherit as class 3, concurring with legitimate children and spouse. Their shares are half those of legitimate children (Article 983). Example: One legitimate child, one illegitimate half-sibling, spouse. Parts: legitimate (2), illegitimate (1), spouse (2). Total 5; legitimate 2/5, illegitimate 1/5, spouse 2/5.

Absence of Legitimate Children but Presence of Spouse and Half-Siblings

Spouse inherits entirely, excluding half-siblings.

No Spouse, No Children, but Ascendants and Half-Siblings

Ascendants inherit entirely, excluding siblings.

Complex Families

In blended families (e.g., from multiple marriages), legitimate children from different spouses are treated equally. Half-siblings from prior relationships may qualify as collaterals only if no closer heirs.

Exceptions and Limitations

Iron Curtain Rule: Illegitimate children cannot represent in the legitimate line (Article 992), affecting half-sibling claims if illegitimate.
Unworthiness: Applies to all heirs (Article 1032), forfeiting shares.
Collation: Advances to children are collated to equalize shares (Article 1061).
Taxes: Succession taxes under the Tax Code apply, but do not alter shares.
Muslim Personal Laws: In the Bangsamoro region, Code of Muslim Personal Laws may supersede for Muslims.
Recent Amendments: Family Code (Executive Order No. 209) and Supreme Court rulings refine but do not overhaul these rules.

Conclusion

Intestate succession safeguards family interests by prioritizing closer relatives. Legitimate children dominate with equal, substantial shares; the surviving spouse enjoys protective concurrence; and half-siblings receive limited, subordinate portions only in remote scenarios. Understanding these rules underscores the importance of estate planning to avoid statutory defaults.