But how?

It just is.

How though?

Gerald is just biologically related to everyone.

Dawg, EXPLAIN.

Gerald's genetics are endowned into every single person that lives on the planet earth.

But how can that be?

You could say he had an extremely high drive to improve upon the population of mankind.

Except he had practically nothing to do with any of this, considering this is never mentioned by any official media at any point in the entire Sonic franchise.

Sega NES confirmed this. Gerald injected a pile of his fluids inside every single homo sapien that ever breathed in the Sonic franchise.