Article 11 to 13, Family Code of the Philippines

Article 11. Where a marriage license is required, each of the contracting parties shall file separately a sworn application for such license with the proper local civil registrar which shall specify the following:

(1.) Full name of the contracting party;

(2.) Place of birth;

(3.) Age and date of birth;

(4.) Civil status;

(5.) If previously married, how, when and where the previous marriage was dissolved or annulled;

(6.) Present residence and citizenship;

(7.) Degree of relationship of the contracting parties;

(8.) Full name, residence and citizenship of the father;

9.) Full name, residence and citizenship of the mother; and

(10.) Full name, residence and citizenship of the guardian or person having charge, in case the contracting party has neither father nor mother and is under the age of twenty-one years.

The applicants, their parents or guardians shall not be required to exhibit their residence certificates in any formality in connection with the securing of the marriage license. (59a)

This article provides the data that must be included in the application for the marriage license. 

Art. 12. The local civil registrar, upon receiving such application, shall require the presentation of the original birth certificates or, in default thereof, the baptismal certificates of the contracting parties or copies of such documents duly attested by the persons having custody of the originals. These certificates or certified copies of the documents by this Article need not be sworn to and shall be exempt from the documentary stamp tax. The signature and official title of the person issuing the certificate shall be sufficient proof of its authenticity.

If either of the contracting parties is unable to produce his birth or baptismal certificate or a certified copy of either because of the destruction or loss of the original or if it is shown by an affidavit of such party or of any other person that such birth or baptismal certificate has not yet been received though the same has been required of the person having custody thereof at least fifteen days prior to the date of the application, such party may furnish in lieu thereof his current residence certificate or an instrument drawn up and sworn to before the local civil registrar concerned or any public official authorized to administer oaths. Such instrument shall contain the sworn declaration of two witnesses of lawful age, setting forth the full name, residence and citizenship of such contracting party and of his or her parents, if known, and the place and date of birth of such party. The nearest of kin of the contracting parties shall be preferred as witnesses, or, in their default, persons of good reputation in the province or the locality. 

The presentation of birth or baptismal certificate shall not be required if the parents of the contracting parties appear personally before the local civil registrar concerned and swear to the correctness of the lawful age of said parties, as stated in the application, or when the local civil registrar shall, by merely looking at the applicants upon their personally appearing before him, be convinced that either or both of them have the required age. (60a)

This Article sets forth the rules by which the civil registrar shall determine whether the parties have required age for marriage.  

Art. 13. In case either of the contracting parties has been previously married, the applicant shall be required to furnish, instead of the birth or baptismal certificate required in the last preceding article, the death certificate of the deceased spouse or the judicial decree of the absolute divorce, or the judicial decree of annulment or declaration of nullity of his or her previous marriage. In case the death certificate cannot be secured, the party shall make an affidavit setting forth this circumstance and his or her actual civil status and the name and date of death of the deceased spouse. (61a)

Article 13 is a substitute for Article 12. This is when either party had been previously married in which case the applicant or applicants, if both parties had been previously married,  shall present in lieu of birth or baptismal certificate, the enumerated listing in Art.13.

The law simply enumerates the contents of an application for a marriage license. Specifically the age and civil status of the applicants. If the applicant is not of legal age as required by the law, or if there is any legal impediment as shown by the application, the Local Civil Registrar would still issue the license, but a notation of the same. A legal impediment is an obstacle to valid marriage, determined by civil authority.

It also requires that if there was a previous marriage that has been annulled or nullified, the party or applicant concerned must attach it to the application in order to prove his capacity to contract marriage. Both parties' capacity to marry is an essential requisite of marriage, the absence of which renders the marriage null and void.

It also provides that if either of the parties was previously married but the spouse is already dead, then the law allows the applicant concerned to execute an affidavit setting forth his or her actual civil status and the name and the date of death of the deceased spouse.

Art. 14. In case either or both of the contracting parties, not having been emancipated by a previous marriage, are between the ages of eighteen and twenty-one, they shall, in addition to the requirements of the preceding articles, exhibit to the local civil registrar, the consent to their marriage of their father, mother, surviving parent or guardian, or persons having legal charge of them, in the order mentioned. Such consent shall be manifested in writing by the interested party, who personally appears before the proper local civil registrar, or in the form of an affidavit made in the presence of two witnesses and attested before any official authorized by law to administer oaths. The personal manifestation shall be recorded in both applications for marriage license, and the affidavit, if one is executed instead, shall be attached to said applications. (61a)

Without the required CONSENT, the marriage is VOIDABLE.

Therefore, the parties to the marriage who are between ages 18 and 21 must secure parental consent. Otherwise it is voidable. (Art. 25 [1] Family Code). 

A parental consent shall be manifested:

1. In writing by the person concerned who personally appears before the Local Civil Registrar; or

2. In the form of an affidavit made in the presence of two (2) witnesses and attested before any official authorized to administer oaths.

So if X and Y got married without the consent of their parents, is their marriage deemed to be invalid under the law?

No. Even if the parties failed to obtain their parents’ or guardian’s consent, their marriage is still considered as valid subject to the right of their parents or guardians to file for the annulment of their marriage within five (5) years from the celebration of the marriage. (Article 47 of the Family Code of the Philippines)

Non-compliance with the requirement of parental consent does not make the marriage invalid or void but merely voidable, which means that the marriage is valid until annulled.

As a result, a petition for the annulment of the marriage may be filed by the parents, guardian or person having substitute parental authority over the party seeking the annulment, in that order, unless after attaining the age of majority, such party freely cohabited with the other and both lived together as husband and wife.

References:
sc.judiciary.gov.ph
http://www.officialgazette.gov.ph
Family Code of the Philippines by Albano, et al.
I also have this blog on September 15, 2018, at this link:
http://thelawexplorer.blogspot.com/2018/09/article-11-family-code-of-philippines.html