Using father's surname when parents not married

magtatanong po ako about sa case ko. I was born out of wedlock in 1985 and my father was not here to sign papers na he is my father so the midwife advised my mom, at sya rin po nag fill up ng form, na maglagay ng fake marriage date para magamit ko ang surname ng father ko. pinapirma nya rin ang mom ko adopting my father's surname sa name nya pagpirma nya kahit di pa sila married. Nagpakasal po sila 2 years after i was born. Then i have 2 other siblings born after that using nga yong real marriage date ng parents ko. My siblings don't have problems with their birth certificate, but mine is quite complicated kasi po sa birth certificate ko mali din spelling ng first name ng tatay ko, from Rolly naging Rely. I want it to get amended kaso yon nga i discovered the inconsistencies. So now ang gusto ko po sana mangyari, maayos yong first name ng father ko from Rely to Rolly at the same time yong marriage date nila sa bc ko. From reading posts I am assuming the marriage date should have been left blank then i should have been legitimated thru subsequent marriage. They weren't married to anyone else before i was born and they are only married to each other up until now and going strong. Please advise on the proper steps to do. Pwede po ba yong mom ko na lang magfile ng petition kaso ayoko po magkaproblema yong mama ko kasi sya po yong pinapirma as informant tapos yong name nya din dun inadopt nya na name ng father ko kahit di pa sila kasal. so it's like from declared legitimate->illegitimate->legitimate by susbequent marriage.No change in my name since ive been using my father's surname but other details need to be amended. Please advise po.

up ko lang po sana ang case ko