This article explains the Philippine rules on succession as they affect (a) children born outside marriage and (b) partners who are not legally married to the decedent. It draws from the Civil Code, the Family Code (as amended), and leading doctrines. It is informational, not legal advice.

1) Key Definitions

Legitimate child – born or conceived during a valid marriage (or otherwise legitimated by law).
Illegitimate child – not legitimate under the law (Family Code simplified the old categories). They have rights to support and succession, but with limits relative to legitimate heirs.
Unmarried partner – a person who lived with the decedent without a valid marriage (sometimes called “common-law” partner). Philippine law does not treat them as a “spouse” for succession.

2) Filiation (Proving the Parent-Child Relationship)

Illegitimate children must prove filiation to claim support or inheritance. Common modes include:

Civil registry: birth certificate naming the parent.
Public/Private document: express admission of filiation.
Open and continuous possession of status: the parent treated the child as theirs.
DNA and other modern evidence: accepted in appropriate proceedings.

Time limits. Actions to claim recognition or to impugn can be subject to prescriptive/procedural rules; however, suits for compulsory shares typically presuppose established filiation. Establish filiation as early and as formally as possible.

3) Surnames and Acknowledgment (practical effects, not shares)

By default, an illegitimate child uses the mother’s surname.
If acknowledged by the father under the statutory process, the child may use the father’s surname.
Acknowledgment does not convert the child into a legitimate child and does not equalize inheritance shares. It only clarifies filiation and enables surname use and support/successional claims.

4) Who Are Compulsory Heirs?

Compulsory heirs are persons who cannot be deprived of their legitime (reserved minimum):

Legitimate children/descendants
Legitimate parents/ascendants (if no legitimate descendants)
Surviving spouse (if there is a valid marriage)
Illegitimate children

Unmarried partners are not compulsory heirs.

5) The “Legitime” and the Free Portion (Overview)

The estate is split into:

Legitime – reserved by law for compulsory heirs.
Free portion – may be disposed of by will to anyone (subject to prohibitions) or, if no will, distributed by intestacy.

Basic legitime baselines:

Illegitimate child’s legitime = one-half (1/2) of a legitimate child’s legitime.
Surviving spouse’s legitime varies by who they concur with (equal to one legitimate child’s share if with legitimate children; other formulas apply in other constellations).

These baselines interact; computations must reflect who actually survives the decedent.

6) The “Iron Curtain Rule” (Article 992, Civil Code)

An illegitimate child cannot inherit ab intestato (by intestacy or representation) from the legitimate relatives of the child’s father or mother, and vice versa. Consequences:

No representation by an illegitimate grandchild in the estate of a legitimate grandparent through the parent.
An illegitimate child inherits from the parent directly, but not from the parent’s legitimate relatives.

This rule is a frequent litigation hotspot—plan estates with it in mind.

7) Intestate Succession Scenarios (No Will)

Below are simplified, high-level patterns. (All examples assume 100% net estate after debts/expenses.)

A. Decedent leaves only legitimate children

The legitimate children share the estate equally.
Illegitimate children, if any, also inherit, each receiving half of what each legitimate child gets.
There is no surviving spouse in this sub-scenario.

Example Heirs: 2 legitimate children (L1, L2) and 1 illegitimate child (I1). Let each legitimate child’s share = x. I1’s share = x/2. Total estate: L1 + L2 + I1 = x + x + x/2 = 2.5x = 100% → x = 40%. Shares: L1 40%, L2 40%, I1 20%.

B. With a valid surviving spouse + legitimate children

Spouse’s intestate share is equal to one legitimate child’s share.
Each illegitimate child still takes half of a legitimate child’s share.

Example Heirs: spouse (S), 2 legitimate children (L1, L2), 1 illegitimate child (I1). Let a legitimate child’s share = x; then S = x, I1 = x/2. Total: L1 + L2 + S + I1 = x + x + x + x/2 = 3.5x = 100% → x ≈ 28.571%. Shares: L1 ≈ 28.571%, L2 ≈ 28.571%, S ≈ 28.571%, I1 ≈ 14.286%.

C. Only illegitimate children, no spouse, no legitimate descendants/ascendants

They share equally among themselves.

D. No descendants, valid spouse + legitimate parents/ascendants

Spouse and legitimate ascendants share per Civil Code formulas (not reproduced in full here).
Illegitimate children are not present in this scenario by assumption; if present, they participate as compulsory heirs with a fixed legitime (half of a legitimate child’s legitime) and the arithmetic changes.

Because combinations can be intricate (e.g., with ascendants, half-blood collaterals, or multiple sets of illegitimate children), do a fresh computation for the actual family tree.

8) Testamentary Succession (With a Will)

A will may favor anyone using the free portion, subject to:

Respect for legitimes of compulsory heirs (including illegitimate children).
Prohibitions (see §11 below).
Form and capacity requirements for validity.

Illegitimate children cannot be disinherited except for a legal cause expressly allowed by law and stated in the will.

9) Rights of Illegitimate Children Beyond Shares

Support: enforceable against parents (and, in some cases, their estates) proportionate to resources and needs.
Use of surname: as noted above when acknowledged.
Representation: generally not allowed into legitimate lines because of the Iron Curtain Rule; they may represent their illegitimate parent in succession from illegitimate relatives.

10) Property Relations of Unmarried Partners (Articles 147 & 148, Family Code)

These rules matter because co-owned property is carved out first before you compute the decedent’s estate for succession.

A. Article 147: Both parties not disqualified to marry

If two people who could legally marry cohabit as spouses without a valid marriage (e.g., purely lack of a license/ceremony), properties acquired by their joint efforts, work, or industry are co-owned—presumed equal shares, unless proven otherwise.
Wages and salaries are included.
Property acquired by one with exclusive funds remains exclusive.
Bad faith (one or both knew of impediments) pushes the case to Article 148.

B. Article 148: One or both parties disqualified to marry (e.g., existing marriage, priestly vow)

Only properties acquired through their actual joint contributions are co-owned, and shares are proportionate to proven contributions.
If both are in bad faith, their forfeitable portions can pass to their common children; in default, to the innocent spouse’s children or the State, per statutory rules.
Criminal laws (e.g., bigamy, concubinage/adultery) may be implicated in these unions; property rules are separate from criminal liability.

Practical effect on succession: When a partner dies, first settle/partition the co-owned property under Art. 147/148. Only the decedent’s share enters the estate for distribution to heirs (children, spouse if any, parents/ascendants, etc.). The unmarried partner does not inherit as a spouse.

11) Can an Unmarried Partner Inherit?

A. By Intestacy (no will)

No. There is no legal right for the surviving partner to inherit as a spouse.

B. By Will

Yes, from the free portion, but subject to:
- Legitime of compulsory heirs (must be respected).
- Public policy prohibitions on gifts to a paramour: Philippine law voids donations and testamentary provisions in favor of a person with whom the donor/testator was guilty of adultery/concubinage at the time (this hits Article 148-type relationships). A partner under Article 147 (both free to marry) is not per se a “paramour”; but the free-portion limit and other rules still apply.

C. Outside Succession

Contract/insurance/benefits designations may allow benefits to flow to a partner, but public policy limits apply to adulterous/concubinage relationships. Always check the policy terms and case law applicable to the relationship’s nature.
Claims under Articles 147/148 are property claims (co-ownership), not inheritance.

12) Children of Unmarried Partners

Children of cohabiting partners are, by default, illegitimate, with the rights described above (support, succession at half the legitime of legitimate children, surname/acknowledgment rules).
Their shares are computed per child, not per “side of the family.”
Filiation proofs and timelines remain critical.

13) Sample Computation Templates

Use these as quick worksheets (replace numbers with actual facts after carving out any Art. 147/148 co-owned properties).

Template 1: Spouse + Legitimate Children + Illegitimate Children

Let L = share of each legitimate child.
Spouse = L.
Each illegitimate child = L/2.
Solve: (# of legit kids × L) + (spouse × L) + (# of illegit kids × L/2) = 100%.
Compute each percentage.

Template 2: Only Illegitimate Children

Divide equally among all illegitimate children (no spouse, no legitimate descendants/ascendants).

Template 3: With Ascendants (no descendants)

Determine if there is a valid spouse. Apply Civil Code formulas for spouse + ascendants.
If illegitimate children exist, incorporate their fixed legitime and re-compute the free portion.

Always subtract debts, taxes, funeral/administration expenses first to get the net estate.

14) Practical Estate-Planning Tips

Make a will that (a) recognizes children (including illegitimate), (b) respects legitimes, and (c) consciously allocates the free portion.
Document filiation early (acknowledgment; accurate civil registry entries).
Title assets properly; keep records of exclusive funds vs joint acquisitions for Art. 147/148.
Insurance/retirement designations: review for compliance with public policy and coordinate with the will.
Consider lifetime transfers within legal limits (void if intended to defeat legitimes or if prohibited by Articles on donations).
Avoid adulterous relationships if planning to benefit a partner; prohibitions can void your intended gifts.
For complex families (multiple sets of children, foreign property, prior marriages), get tailored counsel and, if relevant, explore trust and corporate holding structures recognized under local law.

15) Common Pitfalls

Assuming an unmarried partner is a “spouse” for inheritance—they are not.
Ignoring the Iron Curtain Rule and expecting an illegitimate grandchild to represent a predeceased legitimate child in the grandparent’s estate.
Failing to segregate co-owned property under Art. 147/148 before computing estate shares.
Overlooking debts and taxes that reduce the net estate.
Relying on informal acknowledgments that don’t meet evidentiary standards.

16) Quick Answers

Do illegitimate children inherit? Yes—compulsory heirs; each gets half the share of a legitimate child in the same scenario.
Can an unmarried partner inherit without a will? No.
Can a will leave assets to an unmarried partner? Yes, from the free portion—but void if it benefits a paramour in an adulterous/concubinage relationship; and legitimes must be preserved.
Can an illegitimate child inherit from a legitimate grandparent by representation? No (Iron Curtain Rule).

17) Checklist for Families and Counsel

Identify all potential heirs and their status (legitimate/illegitimate; spouse validly married?).
Prove filiation for each child (documents, records).
Determine co-owned property under Art. 147/148 and partition it first.
Compute legitimes and free portion based on actual survivors.
Verify prohibitions (e.g., gifts to a paramour).
Prepare clear estate documents (will, inventory, titles, policy designations).

Final Note

Philippine succession law is highly formula-driven but fact-sensitive. Small changes in the family constellation (e.g., a predeceased child, an existing valid marriage, acknowledged vs. unacknowledged filiation) can swing the math. When in doubt, run the exact constellation through the templates above—or consult counsel for a precise computation.