As I see it, you need to REALLY find your Bio-Father because all your Scholastic Records are using his Surname; Otherwise, tons of Paper-works will befall you. There is no negotiation for these requirements as follows:
a) if the person is less than eighteen (18) years old, the following shall be required:
i) four (4) copies of the Certificate of Live Birth duly accomplished and signed by the proper parties;
ii) accomplished Affidavit for Delayed Registration at the back of Certificate of Live Birth by the father, mother, or guardian, declaring therein, among other things, the following: • name of child; • date and place of birth; • name of the father if the child is illegitimate and has been acknowledged by him; • if legitimate, the date and place of marriage of parents; and • reason for not registering the birth within thirty (30) days after the date of birth
In case the party seeking late registration of the birth of an illegitimate child is not the mother, the party shall, in addition to the foregoing facts, declare in a sworn statement the recent whereabouts of the mother.
iii) any two of the following documentary evidences which may show the name of the child, date and place of birth, and name of mother (and name of father, if the child has been acknowledged):
• baptismal certificate;
• school records (nursery, kindergarten, or preparatory);
• income tax return of parent/s;
• insurance policy;
• medical records; and
• others, such as barangay captain’s certification.
iv) affidavit of two disinterested persons who might have witnessed or known the birth of the child.
b) If the person is eighteen (18) years old or above.
i) all the requirements for the person who is less than eighteen (18) years old; and
ii) Certificate of Marriage, if married.
2. Delayed registration of birth, like ordinary registration made at the time of birth, shall be filed at the Office of the Civil Registrar of the place where the birth occurred.
3. Upon receipt of the application for delayed registration of birth, the civil registrar shall examine the Certificate of Live Birth presented, whether it has been completely and correctly filled in and all requirements have been complied with.