Actually, Jon does NOT have super-sperm. That's why they have so many kids, they're all the product of in vitro fertilization. And according to the internets, they have some kind of wacky religious beliefs that precluded them from removing any of the embryos so that's why her vagina was clown car on the last go-round.
I'm sorry that I know this and I'm sorry if this ruins the show for you.