A scrutiny of the records would show that petitioners were born during their parents' marriage.

The certificates of live birth would also identify Danilo de Jesus as their father. There is perhaps no presumption of the law more firmly established and founded on sounder morality and more convincing reason than the presumption that children born in wedlock are legitimate.

This presumption indeed becomes conclusive in the absence of proof that there is physical impossibility of access between the spouses during the first 120 days of the 300 days that immediately precede the birth of the child due to the following: (a) the physical incapacity of the husband to have sexual intercourse with his wife; (b) the fact that the husband and wife are living separately in such a way that sexual intercourse is not possible; or (c) serious illness of the husband, which absolutely prevents sexual intercourse.

Quite remarkably, upon the expiration of the periods outlined in Article 170, and in proper cases Article 171, of the Family Code (which took effect on 03 August 1988), the action to impugn the legitimacy of a child would no longer be legally feasible, and the status conferred by the presumption becomes fixed and unassailable.

Thus, applying the preceding pronouncement to the instant case, it must be concluded that the petitioner —who was born on 5 March 1945, or during the marriage of Alfredo Aguilar and Candelaria Siasat-Aguilar and before their respective deaths — has sufficiently proved that he is the legitimate issue of the Aguilar spouses.

As the petitioner correctly argues, Alfredo Aguilar's SSS Form E-1 (Exhibit "G") satisfies the requirement for proof of filiation and relationship to the Aguilar spouses under Article 172 of the Family Code; by itself, said document constitutes an "admission of legitimate filiation in a public document or a private handwritten instrument and signed by the parent concerned."

Petitioner has shown that he cannot produce his Certificate of Live Birth since all the records covering the period 1945-1946 of the Local Civil Registry of Bacolod City were destroyed, which necessitated the introduction of other documentary evidence — particularly Alfredo Aguilar's SSS Form E-1 (Exhibit "G") — to prove filiation. It was erroneous for the CA to treat the said document as mere proof of open and continuous possession of the status of a legitimate child under the second paragraph of Article 172 of the Family Code; it is evidence of filiation under the first paragraph thereof, the same being an express recognition in a public instrument.

To repeat what was stated in De Jesus, filiation may be proven by the admission of legitimate filiation in a public document or a private handwritten instrument and signed by the parent concerned, and such due recognition in any authentic writing is, in itself, a consummated act of acknowledgment of the child, and no further court action is required.

Relative to the said form of acknowledgment, the Court has further held that — given the pronouncements herein made, the Court sees it fit to adopt the following rules respecting the requirement of affixing the signature of the acknowledging parent in any private handwritten instrument wherein an admission of filiation of a legitimate or illegitimate child is made:

1. Where the private handwritten instrument is the lone piece of evidence submitted to prove filiation, there should be strict compliance with the requirement that the same must be signed by the acknowledging parent; and
2. Where the private handwritten instrument is accompanied by other relevant and competent evidence, it suffices that the claim of filiation therein be shown to have been made and handwritten by the acknowledging parent as it is merely corroborative of such other evidence. 

(To be continued)