The problem of unregistered marriages in Indonesia remains a complex issue that raises legal matters, particularly regarding the status of children. In Islamic law, unregistered marriages that fulfil the pillars and requirements of sharia, such as the presence of a guardian, witnesses and the consent are still considered valid, so that children born from them have a clear lineage to their father and obtain basic rights, including inheritance. However, in Indonesia a marriage is considered valid only if it is registered in accordance with Article 2 paragraph (2) of Law Number 1 of 1974 in conjunction with Law Number 16 of 2019. As a result, children from unregistered marriages are often only recognized as having a civil relationship with their mother, unless there is recognition or a court ruling, as affirmed in Constitutional Court Decision Number 46/PUU-VIII/2010. The paper uses a juridical-normative approach with a framework of lineage theory in Islamic law, legality theory in positive law, child protection theory, and progressive legal theory. Data were obtained through a review of literature, legislation, and court decisions. The research findings indicate a dual status for children born into unregistered marriages: legitimate according to religion, but not fully protected by state law. This discrepancy has implications for lineage rights, inheritance, population administration and child protection. The paper concludes that legal harmonization is essential. The state needs to strengthen the marriage confirmation mechanism, and establish marriage registration as an administrative tool to ensure legal child protection.
