[wild speculation] Okay, how about this scenario?
We know that Kal and Lois are each other's soulmates. Maybe all Kryptonians are supposed to have a soulmate, and to mate with their soulmate, if possible. Maybe, for one reason or another, Kryptonians can only procreate with their soulmate? Maybe the Kryptonian woman's body will reject any sperm that doesn't come from her soulmate?
Okay, but nobles may have to marry for different reasons entirely - so that two important noble houses can be joined through matrimony, for example. Maybe nobles aren't usually expected to be able to procreate with their spouses. Maybe there are birthing matrixes for them. Or - how about this? - maybe that is why they have concubines? Maybe they are supposed to find their soulmate by aquiring as many concubines as possible? Or at least, they are supposed to find someone who is at least physically compatible with them, someone whose body will not reject their seed.
But now suppose that a male noble is supposed to react physically to the woman he can have children with. And she is supposed to react physically to him. But in poor Kal's case, this has never happened. Kal has never had the slightest desire to see his wife naked, or to see any of his concubines naked - that is, until he met Lois Lane. And because he hasn't, so far, been turned on by any of the women who, literally, belong to him, he is not yet a father? But now, because Lois makes his heart beat faster and his blood flow stronger, he can? Except the NKers are not likely to accept that their ruler has children by a concubine who is an alien? [/wild speculation]
Okay, that was my take on the fine art of wild speculation. Next contestant, please?
Ann
