“I don’t see why this is such a freaking controversy,” she said. “You have a species that you think is extinct, except for one male specimen. You find a female specimen. She’s fertile. She’s of breeding age. What do you do?”
“That’s incest,” I said.
“Yeah, and if you rearrange the letters in incest and add a few more, you get ‘necessity’,” she said. “If it’s necessary for the survival of their species, they should do it.”
“It’s just wrong,” I said. “He would never do that.”
“He’s dooming his own species to extinction, then,” she said. “It’s wrong of him not to do it. Morally, it’s the first thing he should have thought of when she got off the ship.”
“And what about birth defects?” I asked. “How are they supposed to get a viable breeding population from two people?”
“I don’t know, it looks like they have pretty good genes to me,” she said. “Don’t you think their home planet was the kind of place that would be all eugenic-y and stuff, anyway? And besides, who cares if you have male pattern baldness or even hemophilia when you’re going to be freaking invulnerable anyway?”
“Okay, but what if they have super birth defects? I mean, look at what happens when a clone of him goes wrong,” I said. “They could end up making a breeding population of Bizarros.”
“But look at what happens when a clone of him goes right,” she said. “I’m sure this isn’t a new idea… there was a ton of ‘Superman Family’ stuff Pre-Crisis. Where did all of that stuff come from?”
“Superman wasn’t fucking his cousin Pre-Crisis. Seriously.”
“You just don’t want any of my ships to become canon.”

No explanation or excuse for this one.
It’s loosely inspired by a dream.
Cousin incest is legal in Sweden.
Now you know.
BWA HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA
Heh. I don’t get the last line, but the rest of it is classic.
Also, no reason Supes couldn’t hook up with Power Girl, who is technically not related to him at all. Technically.
Although, personally, I’d rather see PG and Supergirl hook up (yes, I’m aware there’s a wealth of 34 of this available).
Dave: “Ship” is fanficspeak for putting characters in a relationship that didn’t happen in the canon.
Canon is the official story. Harry Potter canon, for example, is all the stuff Rowling wrote. Superman canon would be the stuff that’s published by DC (often, movies are NOT considered to be canon because they change facts and history).
So if the official writers publish a story where this happens, it means the narrator’s fanfiction, which her companion finds disturbing, would become canon, thereby disturbing her companion further.
One wonders why preserving the Kryptonian species is such a big deal. I mean, it’s not like they fill some kind of unique ecological niche, and it’s not like there aren’t plenty of superhero’s to punch random muggers anyway.
Man of steel, woman of steel, bed of Kleenex.
http://itswalky.com/d/20040418.html
It’s not a story about a massive worldwide conservation effort (among other things, they’re an invasive species on earth), it’s about the efforts Kryptonians would or wouldn’t take to preserve their own existence.