Ow, Ann...
I, too, think it's a little weird that Kal doesn't have any offspring yet, but I think speculating that it has to do with that kind of intricate compatibility goes a bit far...
I mean, if it walks like a duck and quacks like a duck, it's duck, right? We've been shown plenty of differences between Humans and Kryptonians, but we *know* none of them have to do with gross anatomy. And I think it's safe to assume from what we know about the Kryptonians we've seen on the show that Kryptonians don't differ that much from Humans on the finer points of anatomy and physiology, either. Unless it was sold really well to me by the writer (which I have no doubt Female Hawk could do, if she really want to go there), I'd have a very hard time accepting the fact that Kryptonians are biologically 'predisposed' to mate with one partner, but not another.
The fact that they have concubines doesn't seem out of the ordinary at all. After all, we know that the nobles' marriages are arranged at birth, and I suppose at least *some* degree of physical attraction between partners is nice to have, when engaging in an intimate relationship. Even among the apparently emotionless Kryptonian nobility.
Maybe the reason Kal doesn't have any offspring yet is simply that he hasn't found the *time* to make it so. The living conditions on NK *are* pretty harsh, after all, and the poor guy's days seem to have been planned down to the minute pretty much since he was born.
The only question, then, remains why Kal has never been otherwise sexually active in his life, either. This is what I was really asking when I wondered what might have happened in his life that made him go 'against the flow' in that regard. After all, since there are concubines involved, one would expect that physical intimacy is assumed to be a normal part of any Kryptonian noble's day. As of this moment, I'm going with the theory that Kal has, at some point in his life, witnessed something that made him decide the concubine system is something he doesn't really want to encourage by fully participating in it himself. But he can't just outlaw it either, because that would likely lead to outrage among his fellow nobles, at the very least, and he does see some advantages to it, as well (in that it enables him to give certain women an extra layer of protection in this harsh society).
