What is necessary for an illigitmate Filipino to establish the right to use the Paternal surname?

Question

My "ex" was conceived, and born out of wedlock. According to the Philippine Family Code she MUST use the surname of her mother. Yetm my ex has used her biological father's surname (supposedly "her" father), even though his entire family says that she has no legal right to do so. If she does not have the legal right, EVERYTHING about her is FRAUDULENT.

Answer 1

Does she live in the US? And if she is here, what can her family say?

I think this might be a better question over in the legal section.

We generally deal with the dead here, not the living.

Good luck,  hope things come out well for you and your ex.

Answer 2

Acknowledgement - term us for giving paternal name to a child, the father is suppose to acknowledge that he is the biological father even out of wedlock. if the mother gives the paternal surname without the acknowledgement of that person and it shows on the child birth certificate, then the civil office commited a big mistake. for whatever reason the name on the childs birth certificate is the legal name that he should use. note some of the actors and actresses have a different name that they use in public but when it comes to legal matter the have to use whatever is on their birth cert.