Answer
Under the Family Code, the filiation of children is established by (1) the record of birth appearing in the civil register or a final judgment, or (2) an admission of filiation in a public document or in a private handwritten instrument signed by the parent concerned (Article 172, applied to illegitimate children by Article 175).
In the absence of these, filiation may be proved by (1) the open and continuous possession of the status of a legitimate or illegitimate child, or (2) any other means allowed by the Rules of Court and special laws — which today includes DNA testing. An illegitimate child has, in general, the same evidentiary means as a legitimate child to prove filiation.
Researching Philippine law? Intellegal brings Philippine case-law search, statute and issuance exploration, multi-dimension case comparison, document visualization, and cited deep-research reports into a single workflow — with every citation traced back to its original source, so you can verify each answer rather than take it on trust. Every authority it surfaces links back to its original provision or decision, so you can open the source and confirm the wording yourself, and save or export the questions and reports you reference most. See the full report for the statutes and cases behind this answer, or explore the related questions below.