It can be difficult to learn more about someone when the earliest record that can be located is a marriage and it seems like they just showed up from nowhere at the courthouse to get married and start making descendants.
Sometimes that first appearance is the first time they’ve actually provided their name to the person writing it in a record. In earlier records (such as census) someone else provided their name, perhaps a parent, older sibling, etc. Is it possible that during that time they were living with a step-parent, foster parent, etc. and their last name was used for the “appearing ancestor?” That marriage where they “appear” could be the first record where they actually provided their name–that of their biological father.
Maybe they were living in the area for years before they got married–just under a last name that you are unaware of.