An Acknowledged Illegitimate Child Has Standing to Challenge a Void Marriage Affecting Their Inheritance Rights

The Thai Supreme Court Judgment No. 2984/2569 addresses an important legal issue concerning the rights of an acknowledged illegitimate child to challenge the validity of their deceased father’s subsequent marriage, where that marriage was entered into while the father was still legally married to another woman.

The central question was whether the child had sufficient legal interest (standing) to petition the court to declare the subsequent marriage void under Section 1497 of the Thai Civil and Commercial Code (CCC), particularly where the validity of that marriage directly affected the child’s inheritance rights.

The Supreme Court held that an illegitimate child acknowledged by their father is entitled to be treated as a descendant under Section 1627 of the CCC and, therefore, as a statutory heir under Section 1629(1) of the CCC. Where a purported marriage affects the distribution of the father’s estate and reduces the child’s inheritance entitlement, the child has a legitimate interest in seeking a judicial declaration that the marriage is void.

This judgment provides important clarification on the relationship between marriage validity, inheritance rights, and the legal standing of family members under Thai law.

1. Background and Facts of the Case

The Plaintiff was born to her biological father and mother, who had lived together as husband and wife without registering their marriage.

The father subsequently registered a marriage with another woman (the first wife) on 9 November 1981. They had no children together.

On 4 September 1986, while his first marriage remained legally registered and no divorce had been obtained, the father registered another marriage with the Defendant.

The father passed away on 22 January 2021.

Although the Plaintiff’s parents had never legally registered their marriage, the father had acknowledged the Plaintiff as his child through several acts, including:

• Allowing the Plaintiff to call him her father.
• Permitting the Plaintiff to use his surname.
• Recording the Plaintiff as his child in the household registration.
• Providing financial support, maintenance, and education.

On 31 October 2022, the Defendant was appointed by the court as the administrator of the father’s estate.

The Plaintiff subsequently filed a lawsuit seeking a declaration that the marriage registered between her father and the Defendant on 4 September 1986 was void, on the ground that her father was still legally married to his first wife when the second marriage was registered.

The Court of First Instance ruled in favour of the Plaintiff and declared the marriage void.

However, the Court of Appeal for Specialized Cases reversed the judgment and dismissed the claim, finding that the Plaintiff did not qualify as an interested person entitled to seek such a declaration.

The Plaintiff appealed to the Supreme Court.

2. Legal Issues Before the Supreme Court

Whether an acknowledged illegitimate child has sufficient legal interest to petition the court for a declaration that their deceased father’s subsequent marriage is void because it was registered while he was still legally married to another person.

3. The Supreme Court’s Reasoning

3.1 An Acknowledged Illegitimate Child Is a Statutory Heir

The Supreme Court first considered the Plaintiff’s legal status as the deceased father’s child.

Although the Plaintiff was born outside a registered marriage, the father had acknowledged her through his conduct, including allowing her to use his surname, recording her as his child in the household registration, and providing financial support and education.

Under the CCC, an illegitimate child acknowledged by their father is deemed to be a descendant in the same manner as a legitimate child.

Consequently, the Plaintiff qualified as a statutory heir under the CCC and was entitled to inherit from her father’s estate.

This established that the Plaintiff had a legally recognized inheritance interest in the deceased’s estate.

3.2 The Subsequent Marriage Violated the CCC

At the time the father registered his marriage with the Defendant on 4 September 1986, his previous marriage, registered on 9 November 1981, had not been dissolved by divorce. Accordingly, the subsequent marriage was prohibited and void under the CCC.

However, the Supreme Court emphasized an important procedural distinction. In the absence of a court judgment declaring the marriage void, the marriage between the father and the Defendant had to be treated as legally existing.

Consequently, the Defendant continued to hold the status of a lawful wife and statutory heir under the CCC.

3.3 The Defendant’s Status Directly Affected the Plaintiff’s Inheritance Rights

The Defendant had relied on her status as the deceased’s lawful wife to petition the court for appointment as administrator of his estate under the CCC. The court had granted that application.

As long as the Defendant continued to be treated as the deceased’s lawful spouse, she was entitled to inherit alongside the deceased’s descendants. This meant that the Defendant would receive an inheritance share equivalent to that of a child.

The Supreme Court recognized that the Defendant’s purported marital status directly reduced the Plaintiff’s potential inheritance entitlement.

The Plaintiff was not merely asserting an abstract interest in the validity of her father’s marriage. Rather, the outcome of the proceedings would directly affect the distribution of the estate to which she was legally entitled.

Accordingly, the Plaintiff had a direct and legally recognizable interest in challenging the marriage.

3.4 A Void Marriage Does Not Create Inheritance Rights as a Surviving Spouse

A marriage that is void does not confer inheritance rights upon the purported spouse in the capacity of a statutory heir.

Therefore, if the court declares the marriage between the father and the Defendant void, the Defendant cannot rely on that void marriage to claim an inheritance share as the deceased’s surviving spouse.

This distinction is significant because the Defendant’s claimed status as a lawful spouse had a direct impact on the Plaintiff’s inheritance rights.

3.5 The Plaintiff Was Not Exercising Her Rights in Bad Faith

The Supreme Court also rejected the argument that the Plaintiff’s claim constituted an exercise of rights in bad faith.

The Plaintiff was the deceased’s child and had not participated in, caused, or been responsible for her father’s subsequent marriage while his previous marriage remained in force.

Her claim was based on the protection of her own lawful inheritance rights.

The Supreme Court therefore found no basis to characterize the Plaintiff’s exercise of her legal rights as being in bad faith.

4. The Supreme Court’s Decision

The Supreme Court held that:

1. The Plaintiff was an illegitimate child acknowledged by her father and was therefore deemed a descendant.
2. The Plaintiff was a statutory heir entitled to inherit from her father’s estate.
3. The father’s subsequent marriage with the Defendant violated the CCC and was void.
4. Until a court declared the marriage void, the Defendant continued to be treated as the lawful spouse and a statutory heir, thereby affecting the Plaintiff’s inheritance entitlement.
5. The Plaintiff consequently had a direct legal interest in seeking a declaration that the marriage was void.
6. The Plaintiff’s exercise of this right did not constitute bad faith.

The Supreme Court allowed the appeal, reversed the Court of Appeal’s judgment, and reinstated the judgment of the Court of First Instance declaring the marriage void.

5. Legal Significance and Practical Implications

This judgment is significant for several reasons.

First, it reinforces the inheritance rights of acknowledged illegitimate children.

Section 1627 of the CCC provides legal protection to children born outside a registered marriage where the father has acknowledged them. Such children are treated as descendants for inheritance purposes and may claim their statutory inheritance rights.

Second, it clarifies who qualifies as an interested person.

The right to challenge a void marriage is not necessarily limited to the spouses themselves. A third party who can demonstrate a direct legal interest arising from the marriage may also have standing to seek a judicial declaration of invalidity.

In this case, the Plaintiff’s inheritance entitlement was directly affected by the Defendant’s purported status as the deceased’s lawful spouse.

Third, it highlights the importance of obtaining a judicial declaration of nullity.

Even where a marriage appears to violate the CCC, the legal consequences of that marriage may continue to affect the parties and interested third persons until the court declares it void.

This is particularly important in estate administration, where the status of a surviving spouse may influence the distribution of inherited assets.

Fourth, it demonstrates the relationship between family law and succession law.

A dispute concerning the validity of a marriage may extend beyond the personal relationship between the spouses. It may also affect the rights of children, statutory heirs, and other persons with legal interests in the estate.

6. Conclusion

Supreme Court Judgment No. 2984/2569 confirms that an illegitimate child acknowledged by their father is entitled to inheritance rights as a descendant.

Where the father’s subsequent marriage was registered in violation of the CCC, and the purported spouse’s continued legal status directly affects the child’s inheritance entitlement, the child qualifies as an interested person and may petition the court to declare the marriage void.

The judgment is an important precedent demonstrating that Thai law recognizes and protects the inheritance interests of acknowledged illegitimate children, including their right to challenge legal relationships that directly prejudice their entitlement to an estate.

7. How Skyinterlegal Can Help

Family disputes involving inheritance rights, multiple marriages, and questions concerning the legal status of children can be legally complex and emotionally sensitive. Understanding your legal position and taking appropriate action at the right time are essential to protecting your rights and interests.

At Skyinterlegal, we provide legal advice and representation in family law, inheritance disputes, estate administration, and civil litigation in Thailand. We assist both Thai and international clients in navigating complex legal matters and resolving disputes in accordance with Thai law.

Our legal services include:

7.1 Legal Advice on Inheritance Rights and Statutory Heirs

We assist clients in determining their legal entitlement to inherit under the Thai Civil and Commercial Code (CCC), including cases involving:

• Children born outside a registered marriage who have been acknowledged by their fathers.
• Disputes concerning the status and inheritance rights of legitimate and illegitimate children.
• Conflicting inheritance claims involving surviving spouses and descendants.
• Disputes concerning multiple marriages and the legal status of a purported spouse.
• Determination of statutory heirs and their respective inheritance entitlements.

7.2 Challenging Void Marriages Under Thai Law

Where a marriage may have been registered in violation of Thai law, we provide legal advice and assistance concerning the validity of the marriage.

Our services include:

• Reviewing marriage registration records and relevant supporting documents.
• Assessing whether a marriage may be void.
• Advising interested persons on their legal standing.
• Preparing court applications and supporting legal documentation.
• Representing clients in proceedings seeking a judicial declaration that a marriage is void.

7.3 Estate Administration and Inheritance Disputes

Disagreements concerning estate administrators, beneficiaries, and the distribution of inherited assets can create significant legal and financial complications.

We assist clients with:

• Applications for appointment of estate administrators.
• Disputes concerning the appointment, authority, and conduct of estate administrators.
• Legal representation in contested inheritance proceedings.
• Protection of beneficiaries’ rights and inheritance entitlements.
• Identification and verification of estate assets.
• Estate administration and transfer of inherited property.

7.4 Litigation and Asset Investigation

Where inheritance disputes involve substantial assets or disagreements over ownership, identifying and protecting estate assets may be essential.

Our firm also provides litigation support and investigative services, including asset searches, property investigations, and assistance with judgment enforcement, where legally appropriate.

Why choose Skyinterlegal?

We understand that inheritance disputes are not simply financial disagreements. They often involve family relationships, personal rights, and assets accumulated over a lifetime.

Our approach combines legal knowledge, litigation support, and investigative capabilities to provide practical solutions tailored to each client’s circumstances.

Whether you are an heir seeking to protect your inheritance, a family member challenging the validity of a marriage, or an interested person involved in estate administration proceedings, our team can help you understand your legal options and determine an appropriate course of action.

Contact Us

If you are facing an inheritance dispute or require legal assistance concerning the validity of a marriage, statutory inheritance rights, or estate administration in Thailand, contact our legal team for an initial discussion of your circumstances.