When navigating an annulment (Article 45, Family Code) or a declaration of absolute nullity of marriage (Articles 35, 36, 40, etc.) in the Philippines, the legal discourse often centers heavily on the custody and support of minor children. However, the dissolution of a marriage triggers complex property, financial, and evidentiary issues that directly involve adult children (those 18 years old and above).

While the term "custody" legally ceases to apply once a child reaches adulthood, Philippine family law maintains strict frameworks governing their financial support, inheritance rights, and roles within the trial.

The Illusion of "Custody": Emancipation and Parental Authority

Under Title IX of the Family Code of the Philippines, child custody is a direct consequence of parental authority (patria potestas). However, this authority automatically expires upon the child's legal emancipation.

Pursuant to Republic Act No. 6809, the age of majority in the Philippines is 18 years old.

Article 236 of the Family Code states: "Emancipation shall terminate parental authority over the person and property of the child who shall then be qualified and responsible for all acts of civil life, save the exceptions established by existing laws in special cases."

Consequently, a trial court handling an annulment lacks the jurisdiction to rule on the custody, care, or visitation rights of adult children. Because they possess full civil capacity, adult children have absolute autonomy. They are legally free to reside with either parent, divide their time between both, or live independently without court oversight.

The Continuation of Financial Support (Sustento) Beyond 18

While parental authority and custody dissolve at age 18, the parental obligation to provide financial support does not automatically terminate. This remains a significant point of intersection between adult children and the annulment process.

1. Educational Support

Under Article 194 of the Family Code, the definition of support (sustento) encompasses everything indispensable for sustenance, dwelling, clothing, medical attendance, and transportation. Crucially, the law extends this to higher education:

Support explicitly includes expenses for "schooling or training for some profession, trade or vocational course, even beyond the age of majority, until the child completes that education or training."
If an adult child is pursuing a college degree or vocational course in good faith and without unreasonable delay, both parents remain solidarily liable to provide support proportionate to their financial resources and the child's necessities (Article 201).

2. Physical or Mental Incapacity

If an adult child suffers from a physical or mental disability that renders them incapable of self-support or gainful employment, the parents' obligation to provide support continues indefinitely, regardless of the child's age.

3. Legal Standing to Sue (Persona Standi in Judicio)

Because an individual gains full civil rights at age 18, an adult child whose higher education or specialized care is being neglected does not need a guardian to act for them. The adult child can file a petition for support or enforcement in their own name against one or both parents. Alternatively, a custodial parent may continue to claim support on behalf of an adult child if that child remains a dependent household member.

The Compulsory Delivery of Presumptive Legitimes

One of the most critical aspects of finalizing an annulment or nullity case is the liquidation and partition of the absolute community of property or conjugal partnership of gains. A key requirement of this process is the mandatory delivery of the children's presumptive legitimes.

Definition: A legitime is the portion of a parent's estate reserved by law for compulsory heirs (such as children) which cannot be freely disposed of. A presumptive legitime is an advance on this inheritance, calculated and delivered while the parents are still alive, triggered specifically by the dissolution of the marriage (Articles 50 and 51, Family Code).
Application to Adult Children: The requirement to compute and deliver presumptive legitimes applies to all common children, whether minor or adult.
The Right to Waive: Unlike minor children, whose rights are strictly protected by the court, adult children have the legal capacity to waive their presumptive legitimes. Article 51 explicitly notes that such a waiver can be validly executed by the child after reaching the age of majority.

Legal Consequences of Non-Delivery

The delivery of presumptive legitimes is a substantive prerequisite for the parents' future civil status. Under Articles 52 and 53 of the Family Code:

The judgment of annulment/nullity, the partition of property, and the delivery of presumptive legitimes must be recorded in the appropriate Civil Registry and Registries of Property.
If a parent fails to record these items and subsequently remarries, that second marriage is void ab initio (void from the beginning).
As affirmed by jurisprudence (such as David v. Calilung, G.R. No. 241036), if the property partition and presumptive legitimes were ordered in the nullity case but left unexecuted, the children—even as adults—retain the right to bring an action before the proper Family Court to enforce the delivery of their assets.

The Evidentiary Role of Adult Children in Annulment Proceedings

Beyond financial and property matters, adult children frequently serve as pivotal witnesses in the annulment trial itself, particularly in cases grounded on Psychological Incapacity (Article 36).

Firsthand Testimony: Because adult children have lived through the breakdown of the household, their testimonies are often considered highly credible and objective. They can provide first-hand accounts of chronic infidelities, abandonment, emotional abuse, or a parent's structural failure to comply with essential marital obligations.
Clinical Assessments: Court-appointed psychologists or psychiatrists regularly interview adult children during the evaluation process. Their insights help professionals establish the legal elements of gravity, antecedence, and incurability required to sustain an Article 36 petition.

Comparative Summary of Legal Status

Legal Domain	Minor Children (Under 18)	Adult Children (18 and Above)
Parental Custody	Mandated by court order; governed by the "best interest of the child" rule.	Extinguished. The adult child possesses full autonomy over their residence.
Financial Support	Absolute, continuous, and automatic.	Conditional. Limited to ongoing higher education/training or instances of physical/mental incapacity.
Presumptive Legitime	Mandatory; cannot be waived by the minor child or parents.	Mandatory, but can be explicitly waived by the child via a legal waiver.
Court Standing	Lacks capacity; must be represented by a parent or guardian ad litem.	Possesses full capacity to sue or defend independently in court.