Short answer: It depends on (1) your marital property regime, (2) whether there is a will, and (3) who the compulsory heirs are. Start by classifying the asset (community vs. exclusive), then liquidate any community property, and only then apportion the decedent’s estate to the heirs under Philippine succession law.

1) First things first: classify the property

Philippine law uses marital property regimes to decide whether an asset is part of the spouses’ common pool or belongs exclusively to one spouse.

A. Absolute Community of Property (ACP) — the default since the Family Code

What it is: In ACP, almost everything either spouse owns at the time of the wedding and what they later acquire becomes community property, unless a legal exclusion applies.
Key exclusions (stay exclusive to the spouse who owns them):
1. Property acquired by gratuitous title (e.g., inheritance or donation) and the donor/testator did not expressly include it in the community;
2. Property for personal and exclusive use (except jewelry);
3. Property acquired before the marriage by a spouse who already has legitimate descendants from a former marriage; the fruits/income of such property are also exclusive.

If the “before-marriage” property doesn’t fall under an exclusion, it is community property in ACP.

B. Conjugal Partnership of Gains (CPG) — by prenuptial agreement or older marriages under the Civil Code

What it is: Each spouse keeps ownership of properties they brought into the marriage; the conjugal partnership owns the gains/fruits produced during the marriage and assets acquired by onerous title (purchase) during the marriage.
Effect on premarital property: A house/land bought before marriage remains that spouse’s exclusive property. The rents/fruits earned during the marriage are conjugal.

C. Complete Separation of Property — by valid marriage settlements

Everything acquired before (and during) the marriage stays with the spouse who acquired it.

Practical tip: Don’t guess your regime—check if there is a prenuptial agreement. If none, and the marriage was celebrated under the Family Code (generally August 3, 1988 onward), ACP is the default.

2) Liquidate first, inherit second

When a spouse dies, you don’t split the asset right away among heirs. You first liquidate any common property:

Under ACP:
- Determine if the premarital asset is community (no exclusion) or exclusive (falls under an exclusion).
- If community: compute net community property (assets minus community debts). One-half goes to the surviving spouse as their share. The decedent’s one-half enters the decedent’s estate for distribution to heirs.
- If exclusive: the entire asset is part of the decedent’s estate (subject to debts, charges, and legitimes).
Under CPG:
- The premarital asset is exclusive. Only conjugal gains/fruits are shared and must be liquidated; the exclusive property (less its personal obligations, if any) is part of the decedent’s estate.
Under Separation:
- No community to liquidate. The premarital asset is the decedent’s exclusive property and goes straight to the estate (after debts/charges).

3) With or without a will (testate vs. intestate)

A. If there is a will (testate succession)

The testator may give property by will, but compulsory heirs have legitimes (minimum shares the law reserves). A will cannot impair these.
Compulsory heirs include:
- Legitimate children/descendants;
- In their absence, legitimate parents/ascendants;
- The surviving spouse;
- Illegitimate children (entitled to legitimes);
- In special cases, acknowledged natural/adopted children per applicable rules.
The free portion (what’s left after setting aside legitimes and charges) is distributed according to the will.

B. If there is no will (intestate succession)

Distribution follows fixed orders of intestacy. Very briefly:

If the decedent leaves legitimate children/descendants:
- They inherit in equal shares among themselves;
- The surviving spouse inherits as if one child (i.e., generally an equal share with each legitimate child).
- Illegitimate children also inherit, with shares given by law alongside the above.
If there are no descendants but there is a surviving spouse and legitimate parents/ascendants:
- The spouse and ascendants share the estate as provided by the Civil Code (both are compulsory heirs).
If there are no descendants, no ascendants:
- The surviving spouse may succeed with collateral relatives (siblings, etc.) or alone if there are none—rules vary by degree.
If there are no eligible heirs:
- The State succeeds by escheat.

Important: The marital regime affects what enters the estate, not who the heirs are. Heirs are determined by succession law; the regime determines which assets (and how much of them) are available for inheritance.

4) Worked examples

These are simplified illustrations and ignore taxes/fees. Always apply debts, charges, and legitimes first.

Example 1 — ACP, premarital house (no exclusion), no will, spouse + two legitimate children

Step 1 (Classify): House acquired before marriage, no exclusion → community property in ACP.
Step 2 (Liquidate): Net value ₱10,000,000 → ₱5,000,000 to surviving spouse (community share), ₱5,000,000 is estate.
Step 3 (Intestate shares): Heirs = spouse + 2 legitimate children. They generally share the estate equally as if the spouse were another child:
- Spouse: ₱5,000,000 (community share) + ₱1,666,666.67 (estate share)
- Child A: ₱1,666,666.67
- Child B: ₱1,666,666.67

Example 2 — CPG, premarital condominium exclusive, will favors a sibling; spouse + one legitimate child survive

Step 1 (Classify): Premarital condo is exclusive to decedent under CPG.
Step 2 (Estate): Entire condo value (net of debts) enters estate.
Step 3 (Testate limits): The will cannot reduce legitimes of the child and surviving spouse. The sibling can receive only from the free portion after setting aside legitimes.

Example 3 — ACP, premarital lot inherited before marriage (gratuitous title) → excluded

Step 1 (Classify): Inheritance before marriage = exclusive under ACP.
Step 2 (Estate): Entire (net) value goes to estate.
Step 3: Heirs get shares per testate/intestate rules. The surviving spouse does not first take a community half because the lot is not community.

5) Special issues to watch out for

Co-mingling & improvements: If an exclusive premarital asset is improved with community funds (ACP) or conjugal funds (CPG), the community may have a reimbursement/credit or lien for the value added or expenses advanced. Keep records.
Fruits, rents, dividends:
- ACP: fruits of exclusive property generally belong to the community, except fruits of property excluded under the “former-marriage descendants” rule.
- CPG: fruits during the marriage are conjugal.
Family home: It may be part of the community (ACP) or conjugal (CPG), and is subject to special protections and exemptions; however, on death it still forms part of the estate subject to those protections.
Property registration (Torrens title): Title presumes ownership but does not conclusively decide classification. Courts look at when and how the asset was acquired and the governing regime.
Foreign property / foreign marriages: Philippine conflict-of-laws rules may apply; classification often follows the law of the domicile or law of the place depending on the issue, but succession to immovables generally follows the law of the situs.
Reserva troncal (lineal reserve): Property received by gratuitous title from an ascendant or relative in the direct line, and then transmitted to a descendant and subsequently to a collateral within certain conditions, may need to return to the line it came from. This can constrain who ultimately receives a gratuitously-acquired premarital asset.
Donor/testator conditions: A donation or inheritance can expressly exclude the property (or its fruits) from the community and may impose conditions that bind successors.
Creditors’ rights: Before distribution, settle debts and charges against the community (if applicable) and the estate. Heirs inherit net of liabilities; liabilities do not vanish.
Illegitimate children & acknowledgment: Shares depend on filial status and recognition. Documentary proof (e.g., birth certificates, judgments) often matters in the proceedings.
Second families / prior marriages: The ACP exclusion for a spouse who already has legitimate descendants from a former marriage can keep that spouse’s premarital property exclusive, which meaningfully changes who benefits when that spouse dies.

6) How to analyze a real case (checklist)

Identify the marital regime: ACP default? CPG or Separation by prenup?
Classify the asset: Was it acquired before marriage? If ACP, does an exclusion apply?
Liquidate the community/conjugal partnership (if any): compute the surviving spouse’s share first.
Determine who the heirs are (compulsory heirs; presence of will or not).
Compute legitimes and set aside the free portion (if testate).
Account for credits/reimbursements, debts, taxes, and expenses.
Prepare supporting documents (titles, tax declarations, marriage certificate, birth certificates, prenup, will, donor/testator conditions).

7) FAQ

Q: If I bought a condo before marriage (no prenup), does my spouse automatically inherit it all when I die? A: Not necessarily. Under ACP, that condo likely became community property (unless excluded), so your spouse first takes their community half. The other half is shared by heirs (including the spouse again, with children or other heirs). Under CPG or Separation, the condo would be exclusive, fully forming part of your estate (again, shared under succession rules).
Q: What if the premarital property was inherited from my parent before I married? A: Under ACP, that’s generally exclusive, so it does not get halved as community property before succession.
Q: Do children from a prior marriage affect classification? A: Yes. Under ACP, a spouse’s property acquired before the current marriage remains exclusive if that spouse has legitimate descendants from a former marriage—including its fruits.

Bottom line

To know who inherits a property acquired before marriage, you must first know what that property is in the eyes of the law (community vs. exclusive). After proper liquidation (if applicable), distribute the estate to compulsory heirs under either testate or intestate rules. Because small facts (prenups, donor’s conditions, prior families, improvements) can flip the result, formal advice with the documents in hand is wise for any real case.