(A legal article in Philippine context)

1) Overview: adoption reshapes family and succession

In Philippine law, adoption is not just custody—it creates a legal parent-child relationship. Once a child is validly adopted, the child becomes a legitimate child of the adopter(s) for almost all legal purposes, including succession (inheritance). That has direct effects on the shares of the adopter’s biological children, other relatives, and even the adopted child’s ties to the biological family.

The governing framework comes mainly from:

the Civil Code rules on succession (legitime, compulsory heirs, intestacy, free portion),
the Family Code and the Domestic Adoption Act (RA 8552) on the effects of adoption, and
special rules affecting illegitimate children and legitimes.

2) Key concepts you must understand first

A. Compulsory heirs and legitime

A compulsory heir is a person the law protects from disinheritance by reserving a minimum share called legitime. You cannot give away the entire estate by will if you have compulsory heirs.

In Philippine practice, the most important compulsory heirs are:

legitimate children and descendants,
illegitimate children,
the surviving spouse, and
in some cases, legitimate parents/ascendants (when there are no descendants).

B. Testate vs. intestate succession

Testate: the decedent leaves a will, but the will must respect legitimes.
Intestate: no valid will (or will doesn’t cover everything), so the law determines who inherits.

C. “Legitimate child” status is everything

Many inheritance rules turn on whether the heir is treated as legitimate or illegitimate. Adoption’s biggest inheritance impact is that it generally places the adoptee in the legitimate-child category vis-à-vis the adopter(s).

3) Adopted child’s status: treated as a legitimate child of the adopter

A. As to the adopter(s)

A validly adopted child is, in general, considered a legitimate child of the adopter(s). That means the adoptee:

is a compulsory heir of the adopter(s), and
is entitled to a legitime like any legitimate child.

Practical result: An adopted child and a biological legitimate child of the adopter usually inherit equally from the adopter, unless a specific legal rule changes the picture (e.g., presence of illegitimate children, surviving spouse, special dispositions, etc.).

B. As to the adopter’s relatives (ascending and collateral lines)

Because adoption creates a parent-child relationship, the adopted child typically gains succession rights in the adopter’s line, similar to a legitimate child. This matters especially in intestacy, where kinship and lines determine who gets called to inherit.

4) What happens to inheritance rights from the biological family?

A. General effect: severance of legal ties (with important nuance)

A common effect of adoption is that it cuts the legal relationship between the child and the biological parents for most purposes, replacing it with the adoptive relationship.

Inheritance consequence (general rule):

The adopted child’s right to inherit from the biological parents under intestacy is generally extinguished, because the legal parental tie is replaced.

However, Philippine adoption law and succession discussions often emphasize protecting the child’s welfare, and real-life outcomes can depend on:

the type of adoption (domestic vs. other contexts),
whether the inheritance claim is under intestacy or a will, and
whether the disposition is a voluntary grant (a biological parent can still give property by donation or will, subject to legitime rules vis-à-vis their own compulsory heirs).

B. Biological family can still benefit the adoptee by will or donation

Even if the adoptee is no longer a compulsory heir of the biological parents (as a general succession effect), a biological parent may still give property to the adoptee via:

donation inter vivos, or
testamentary disposition (will), subject to the biological parent’s own compulsory heirs and legitimes.

So the adoptee may still receive property from the biological family, but more as a matter of voluntary disposition, not compulsory intestate entitlement.

5) How the adopted child shares with the adopter’s biological heirs

A. Adopted child vs. legitimate biological children of the adopter

In the adopter’s estate:

An adopted child is generally treated as a legitimate child, so the adoptee shares equally per capita with the adopter’s legitimate biological children.

Example (intestate, simplified): Adopter dies leaving a spouse and three children: two biological legitimate children + one adopted child.

The adopted child is counted as a legitimate child.
The children’s shares among themselves are equal, with the spouse’s share determined by the Civil Code rules for surviving spouse with legitimate children.

B. Adopted child vs. illegitimate children of the adopter

If the adopter leaves illegitimate children, succession becomes more nuanced because Philippine law assigns different legitimes for illegitimate children compared with legitimate children.

General succession principle (conceptual):

Illegitimate children are also compulsory heirs but typically receive a fractional share relative to legitimate children under legitime rules.
The adopted child, being treated as legitimate, is grouped with legitimate children in computing legitimes.

Practical result:

The adopted child’s presence increases the “legitimate children pool,” which can affect proportional computations—especially when the estate must satisfy the legitimes of legitimate children, illegitimate children, and the surviving spouse.

C. Adopted child vs. surviving spouse

The surviving spouse is a compulsory heir in many scenarios. The spouse’s share depends on what other heirs exist (legitimate children, illegitimate children, ascendants).

The adopted child’s status as “legitimate” typically places the case in the rule set for surviving spouse + legitimate children, which usually means:

spouse inherits a share alongside the legitimate children.

D. Adopted child vs. adopter’s parents (ascendants)

If the adopter leaves children, ascendants generally do not inherit by intestacy because descendants exclude ascendants. Since the adopted child counts as a child, the adoptee’s existence may:

exclude the adopter’s parents from inheriting in intestacy, and
restrict the adopter’s ability to leave them more than the free portion if legitimes must be respected.

6) Intestate succession: the adopted child is “in the line”

In intestacy, the law calls heirs in an order. Because the adopted child is treated as a child of the adopter:

the adopted child is in the first line (descendants), and
participates like a legitimate child would.

Representation and descendants of the adopted child

If the adopted child dies ahead of the adopter, questions can arise about whether the adopted child’s own descendants can “step into the shoes” of the adoptee via representation. As a conceptual matter:

representation is generally allowed in the descending line in appropriate cases, and
since the adoptee stands as a child in the adoptive line, the adoptee’s descendants may be positioned to represent within that line, subject to the usual succession requirements.

7) Testate succession: wills must respect legitimes

Even if the adopter makes a will, the adopted child cannot be deprived of the adopted child’s legitime unless:

there is a legally valid disinheritance based on lawful causes and proper form, or
other exceptional rules apply.

A. Can an adopter disinherit an adopted child?

Conceptually, yes—if the adopted child is treated as a legitimate child for succession, then disinheritance rules for compulsory heirs apply. Disinheritance is strictly construed: it must be:

for a cause allowed by law, and
done in the manner required (typically expressly in a will).

B. Can the adopter “favor” biological children over the adopted child?

Only within the free portion. Legitimes act as a floor:

The adopted child must receive at least the adopted child’s legitime.
Beyond that, the adopter can allocate the free portion, subject to other compulsory heirs’ legitimes.

C. Preterition risk (unintentionally omitted compulsory heir)

If a will omits a compulsory heir in the direct line (like a child) in a way that legally counts as preterition, the effect can be severe (often annulling the institution of heirs while preserving legacies/devises insofar as not inofficious). For practical drafting:

adopted children should be explicitly acknowledged in wills to avoid succession disputes.

8) Collateral and extended-family disputes: common Philippine scenarios

A. Siblings and other relatives contesting the adopted child’s share

A common dispute is when the adopter’s siblings (or other relatives) claim that the adopted child is “not really family.” Legally, adoption creates the parent-child relationship; thus:

the adopted child inherits in the adopter’s line and can exclude collateral relatives in intestacy.

B. Property acquired before adoption

Inheritance rights attach to the decedent’s estate at death, not when property was acquired. So whether the adopter obtained property before or after adoption usually doesn’t matter for succession—unless property classification issues arise (e.g., conjugal/community property vs. exclusive property).

C. Conjugal/community property implications

In many estates, a large part of property is not purely “the decedent’s.” You must first determine:

what belongs to the surviving spouse as their share of the marital property regime, and
what comprises the decedent’s net estate for distribution to heirs.

Adopted child’s inheritance applies to the decedent’s share, not to the spouse’s separate share.

9) “Double inheritance” concerns: can an adopted child inherit from both adoptive and biological parents?

In practice, people worry that an adoptee might inherit from:

the adoptive parents (as a legitimate child), and
the biological parents (as a biological child).

As a general succession structure, adoption is designed to substitute the adoptive relationship for the biological parental tie in law, which usually prevents “automatic” intestate inheritance from the biological parents. Still, a biological parent may voluntarily transfer property to the adoptee through:

donation, or
will, subject to legitime limits in that biological parent’s own estate.

So the adopted child can end up receiving property from both families, but usually not as an automatic compulsory-heir package in both lines.

10) Special situations and edge cases

A. Relative adoption / step-parent adoption

If a step-parent adopts a child, succession consequences generally follow the same adoption effects as to the adopting step-parent. The relationship with the non-adopting biological parent typically remains (especially where that parent retains parental rights), but inheritance analysis becomes fact-sensitive:

Who is the legal parent at the time of death?
Are parental rights intact?
What does the adoption decree provide?

B. Void or defective adoption

If adoption is invalid, inheritance rights based on adoption may fail, and parties may revert to biological succession rules. In estate disputes, challengers sometimes attack the adoption’s validity; courts then focus on:

jurisdiction, consent, procedure, and
the finality of the adoption decree.

C. Adoption rescission and its effect

Domestic adoption law has mechanisms affecting the adoption relationship under certain circumstances. If the adoption is legally undone, succession consequences can shift. Estate planning should consider whether a rescission/termination occurred and its timing relative to death.

D. Simulated births / late registration issues

In Philippine practice, paper irregularities (late registration, simulated births later corrected, etc.) often complicate inheritance. The key is determining the legally recognized filiation/adoption status at death and whether records have been lawfully rectified.

11) Practical guidance: how to analyze any case quickly

Step 1: Identify relationships and statuses

Who are the children? legitimate / illegitimate / adopted?
Is there a surviving spouse?
Are ascendants alive?

Step 2: Determine the property regime and net estate

Separate the spouse’s share (community/conjugal) from the decedent’s estate.

Step 3: Determine whether succession is testate or intestate

If there is a will, check validity and compliance with legitimes.
If none, apply intestacy order of heirs.

Step 4: Compute legitimes and the free portion

Ensure compulsory heirs (including the adopted child) are not deprived.

Step 5: Watch for litigation triggers

omitted compulsory heir,
suspicious transfers,
conflicting certificates/records,
disputes over legitimacy/illegitimacy/adoption validity.

12) Takeaways

An adopted child is generally treated as a legitimate child of the adopter(s) and is therefore a compulsory heir entitled to a legitime.
Biological legitimate children and adopted children typically share equally in the adopter’s estate (subject to adjustments when there are illegitimate children and a surviving spouse).
Adoption generally redirects intestate inheritance rights away from the biological parents and into the adoptive line, while still allowing biological parents to benefit the adoptee by will or donation within legitime limits.
In contested estates, the biggest determinants are:
- the adoptee’s legal status (valid adoption decree/records),
- the presence of other compulsory heirs (especially spouse and illegitimate children), and
- whether there is a valid will respecting legitimes.

If you share a sample family tree (e.g., adopter dies leaving spouse + X biological children + Y adopted children + Z illegitimate children), I can lay out the likely heir classification and the logical distribution framework step-by-step under Philippine succession rules.