How to change surename of birth certificate when registered with maiden's family name?

We want to get marry late this year. Ang family name ng boyfriend ko ay family name ng mother nya nakaregister sa birth certificate nya. Pero mula sapol, family name ng father nya ang gamit nya. Lahat ng documents (like baptismal certificate, elementary diploma, high school diploma at TOR sa college) gamit nyang family name ay yung sa father nya. 2nd year college sya nang magkuha ng birth certificate nang pagkuha nya, family name nang mother nya naka-appear na family name nya. Gusto nyang palitan family name nya, gamitin nya yung nasa lahat ng documents nya, yung apelyido ng father nya. Gusto nya, apelyido ng father nya gamitin namin kung makasal na kami. Paano po? Hindi namin alam nasaan na father nya. Ipinanganak sya ng May 7, 1990. Posible pa bang mabago apelyido nya kung wala na father nya? Pakitulong po. Para po makasal kami. Maraming salamat po.

The father has to acknowledge the child first.

Is there an affidavit of acknowledgment?

Thank you for the reply Atty. No, we do not know where is his father now. Is it still possible for us to carry the family name of his father since all his documents were named with his father's family surename? Thank you once again.

They will need the affidavit of the father for you to be able to change his name in the birth certificate.

Is there any other way Atty.? What about late registration? Someone told me to about it. Would that be posible for us?

The affidavit is a requirement for late registration. Anything you will simulate without the real father's participation is ILLEGAL.