There's also the well-worn trope of making up origin stories for real historical people that suit the needs of the mythology. Take Jesus for example: He was born poor, to satisfy one group of the target audience. But he was of royal lineage, Joseph being of the house of David. Add to that the divine parentage and viola, you have a perfect origin story. Hercules and Dionysus have similar backstories. But of course lots of historical people also get this sort of treatment. Lenin, for example was born of a well off gentry, but the communist party invented a humble origin story for him, that glossed over that. Washington has a whole slew of stories about him. Name any person who went from ordinary origins to become a great leader, and chances are that someone tweaked his biography.