....OKay, would an earth genasi be a descendant of someone banged by an earth elemental or be half elemental himself?

You're sort of thinking of it in weird terms. An Genasi would either be the descendant of someone who had a child with a creature from the elemental plane of Whatever, or the servant of one of the Elemental deities. This isn't restricted to just plain Elementals, but shit like Sylphs and other stuff.

A Half-Elemental is something different entirely.

PS. You're disgusting!

I wanted to keep it short and concise.

:oops: