1) Why this topic gets complicated fast

When a parent dies, what each child is entitled to depends on (a) the child’s legal status (legitimate, illegitimate, legitimated, adopted), (b) whether there is a surviving spouse, (c) whether there is a will, and (d) what property is actually part of the “estate” after separating out the shares of a spouse or cohabiting partner under the property regime.

A common real-world pattern looks like this:

Children from a previous marriage (usually legitimate), and
Children from a later live-in relationship (often illegitimate, unless later legitimated), and sometimes
A surviving spouse (from a valid marriage), and/or a surviving cohabiting partner (not a spouse).

Each of those statuses has different consequences in succession.

2) The basic framework: succession, compulsory heirs, legitime

Philippine succession law is built around compulsory heirs and legitime.

A. Compulsory heirs (who cannot be totally disinherited)

As a rule, the following are compulsory heirs:

Legitimate children and descendants
Illegitimate children and descendants (with different quantitative shares)
Surviving spouse (if there is a valid marriage)
Legitimate parents/ascendants (when there are no legitimate descendants)

A live-in partner (without a valid marriage) is not a compulsory heir.

B. Legitime (the protected portion)

Even if there is a will, the decedent cannot freely give away everything. A portion of the estate—the legitime—is reserved by law for compulsory heirs. A will generally operates only over:

the free portion, and
any dispositions that do not impair legitimes.

Key effect: Children from a first marriage and children from a live-in relationship can both be compulsory heirs (if filiation is established), but their shares differ depending on legitimacy and concurrence.

3) Child classifications that matter most

A. Legitimate children

A child is generally legitimate if conceived or born during a valid marriage of the parents. Legitimate children have the strongest successional protection and typically receive full shares relative to other children.

Children from a previous marriage are typically legitimate (assuming that prior marriage was valid and the child was born during it).

B. Illegitimate children (common in live-in setups)

Children conceived and born outside a valid marriage are generally illegitimate, even if the parents lived together for years.

Inheritance rule in broad strokes: an illegitimate child’s legitime is generally one-half of that of a legitimate child (subject to the particular mix of heirs).

C. Legitimated children (a “conversion” in limited cases)

A child born before the parents’ marriage can become legitimated if:

the parents subsequently marry each other, and
at the time of conception, there was no legal impediment for them to marry.

Practical consequence: In a typical “previous marriage still subsisting” situation, there was an impediment—so later marriage may not legitimize earlier children conceived while one parent was still married to someone else.

D. Adopted children

A legally adopted child is treated, for succession purposes, essentially as a legitimate child of the adoptive parent(s). Adoption can dramatically alter inheritance outcomes because the adopted child competes as a legitimate heir in the adoptive family line.

E. Children in void/voidable marriage situations (where “previous marriage” issues appear)

If a marriage is voidable (annullable), children conceived/born before the decree of annulment are generally treated as legitimate.
If a marriage is void (e.g., bigamous), children are generally illegitimate, with notable exceptions in specific statutory situations recognized in family law.

Because these categories are fact-sensitive, the exact status often depends on the precise ground and timing of judicial declarations.

4) The often-missed step: what property is actually in the estate?

Before dividing inheritance, you must identify the net estate—and that requires separating out shares that do not belong to the decedent alone.

A. If the decedent had a valid spouse

Depending on the marriage settlement (and date/context), properties may fall under:

Absolute Community of Property (ACP), or
Conjugal Partnership of Gains (CPG), or
Separation of property (by agreement/court).

Workflow:

Determine which properties are community/conjugal versus exclusive.
Allocate the spouse’s share (often half of community/conjugal, but confirm classification).
Only the decedent’s share goes into the estate for inheritance division.

B. If the decedent had only a live-in partner (no valid marriage)

The live-in partner is not an heir by default, but may own property with the decedent under co-ownership rules for unions in fact.

Family law recognizes property consequences for cohabitation, commonly discussed under:

Union where both are free to marry each other (often treated like co-ownership of acquisitions through joint efforts), versus
Union with an impediment (e.g., one party is married to another), where property rules are generally less favorable to the partner and may depend on actual contributions and good faith.

Critical point: The partner’s property share is taken out first as an ownership matter. What remains as the decedent’s share becomes the estate to be inherited by heirs (children, spouse if any, etc.).

5) Who inherits when there is NO will (intestate succession)

Intestate succession is common when families delay estate planning. The order and sharing rules depend on which heirs survive.

Scenario 1: Decedent leaves children (no surviving spouse)

Legitimate children inherit the estate in equal shares.
Illegitimate children also inherit, but typically at one-half the share of a legitimate child when they concur.

Example (simplified illustration): Estate = ₱10,000,000; heirs = 2 legitimate children (L1, L2) + 2 illegitimate children (I1, I2). Think in “units”: legitimate = 1 unit each; illegitimate = 0.5 unit each. Total units = 1 + 1 + 0.5 + 0.5 = 3 units. Each unit = ₱10,000,000 / 3 = ₱3,333,333.33

L1 = ₱3,333,333.33
L2 = ₱3,333,333.33
I1 = ₱1,666,666.67
I2 = ₱1,666,666.67

(Real cases can vary with other heirs, property regime deductions, and legitime computations where a will exists—but this is the common intestate intuition.)

Scenario 2: Decedent leaves children AND a surviving spouse (valid marriage)

The surviving spouse is a compulsory heir and generally shares with the children (the precise allocation depends on the combination of legitimate/illegitimate children and the applicable Civil Code provisions). As a practical rule-of-thumb in many common setups:

The spouse typically competes “like a child” with legitimate children in certain concurrences, while
Illegitimate children still generally carry the half-share relationship relative to legitimate children.

Because spouse-child concurrence can change the math, this is where professional computation is especially important.

Scenario 3: Decedent leaves no children, but leaves parents/ascendants and/or spouse

If there are no descendants, the line moves up to ascendants (legitimate parents) and/or the spouse. Illegitimate children (if any) will still be considered descendants; if they exist, you’re not in this scenario.

6) If there IS a will (testate succession): what can and cannot be done

A. You cannot disinherit compulsory heirs casually

A will cannot simply “cut off” compulsory heirs unless there is a legal cause for disinheritance and strict formalities are followed. Even then, disinheritance is commonly litigated.

B. The will controls only the free portion

A parent can:

Recognize heirs and distribute the free portion creatively, but
Must respect each compulsory heir’s legitime.

C. Special caution: gifts to a live-in partner when the relationship was legally disqualified

Philippine civil law contains rules that can invalidate donations and even testamentary dispositions in favor of a person with whom the testator was in an adulterous/concubinage relationship at relevant times, as well as other disqualifications to inherit.

Practical takeaway: If the decedent tried to “leave everything” to a live-in partner while still married to someone else (or in a legally prohibited relationship), parts of that plan may be void or contestable, and compulsory heirs may successfully challenge it.

7) Establishing a child’s right: filiation and proof (this wins or loses cases)

A child—especially one from a live-in relationship—must be able to prove filiation to inherit as a child of the decedent.

Common proof routes include:

Birth certificate naming the parent (with proper acknowledgment)
Public documents or private writings acknowledging paternity/maternity
Open and continuous possession of the status of a child (fact-based)
Judicial action to establish filiation (paternity cases)

Important: Using the father’s surname (including under later administrative mechanisms) is not the same as automatically guaranteeing inheritance; inheritance depends on legal filiation, not just social usage.

If other heirs dispute filiation, inheritance may be delayed until the issue is resolved.

8) Children from previous marriages vs children from live-in partnerships: how they compete

A. Previous marriage children (often legitimate)

They typically inherit as legitimate children and receive full legitime shares.

B. Live-in partnership children (often illegitimate unless legitimated)

They inherit as compulsory heirs but typically at half shares relative to legitimate children when they concur.

C. If the parent later marries the live-in partner

The children may become legitimated only if the parents were free to marry each other at the time of conception.
If one parent was still married to someone else at conception, legitimation usually does not apply.

D. If the “previous marriage” was actually void or later declared void

Then the “legitimate” status of children and the rights of the supposed spouse can be more complex. Children may still be protected under specific rules, but you must identify:

the ground and timing of nullity/annulment,
whether the marriage was voidable vs void,
and whether the law treats the children as legitimate in that category.

9) The live-in partner: what they can get (and what they usually cannot)

A. They are not an heir by default

A live-in partner (not married to the decedent) has no automatic inheritance right by intestacy.

B. They may have property rights as a co-owner

They may be entitled to a share of certain properties acquired during cohabitation, depending on:

whether both were free to marry,
contributions (money, labor, industry),
good faith,
and how the property was acquired.

That share is not “inheritance”—it is ownership.

C. They may receive something by will—but subject to limits and disqualifications

Even with a will:

legitimes must be respected, and
disqualification rules (e.g., adulterous/concubinage contexts) may render dispositions void or challengeable.

10) Common disputes and how courts typically see them

Dispute 1: “The live-in children shouldn’t inherit because the relationship was immoral.”

Inheritance rights flow from parent-child relationship, not from approval of the parents’ relationship. If filiation is established, the child’s successional rights attach (though the child’s classification—legitimate vs illegitimate—still affects shares).

Dispute 2: “The live-in partner gets nothing, so they should be evicted from the house immediately.”

Even if not an heir, the partner may have:

a co-ownership interest in the house, or
rights as a possessor in good faith (fact-dependent), so ejectment/partition often requires proper proceedings.

Dispute 3: “The deceased left a will giving everything to the live-in partner.”

Compulsory heirs can bring an action for reduction of inofficious dispositions (i.e., dispositions that impair legitimes) and may also challenge capacity/disqualification issues.

Dispute 4: “The first family says the second family’s children are not acknowledged.”

This becomes a filiation case. If unresolved, estate settlement can stall for years.

11) Practical roadmap for families (what to do, in order)

Identify heirs (all children, spouse if any) and gather proof of filiation.
Classify relationships (valid marriage? cohabitation? impediments?).
Inventory properties and liabilities.
Determine what belongs to the estate after allocating spouse/partner ownership shares.
Check for a will and validate formalities.
Compute legitimes/free portion (if testate) or apply intestate sharing rules.
Settle the estate (judicial or extrajudicial when legally allowed), pay taxes/fees, and transfer titles.

12) Key takeaways (the rules people usually need most)

Children from a previous valid marriage are usually legitimate heirs with full shares.
Children from a live-in partnership are commonly illegitimate heirs and generally inherit at half the share of a legitimate child when they concur.
A live-in partner is not an heir by default, but may own property through co-ownership rules—this is separate from inheritance.
A later marriage can legitimate children only in limited conditions (notably, no impediment at conception).
Wills cannot defeat legitimes, and certain dispositions to a legally disqualified partner may be void/contestable.
Proof of filiation is often the make-or-break issue for children from non-marital unions.

This article is for general legal information in the Philippine setting and is not a substitute for advice from a lawyer who can review documents, timelines, and property titles.