Best post header ever.  Good question though...  It would make sense to allow it, but then maybe apply some negatives.  I don't know there are pros and cons for allowing it and not allowing it.  I would assume they won't allow it.

I have to admit that the idea of Channelers breeding is amusing. But, to keep it realistic, isn't it necessary to add a big random factor that renders the process pointless except if applied on many generations?

But more seriously, I'm not sure that in-breeding would pass the 'politically correct' gate, but I agree it would be nice if there was some way to keep away from all the marriage/alliance/dowry stuff if the player chooses to, without being too much at a disadvantage.

The concept of incest doesn't really phase me one way (or the other ).  I'd rather it be a robust system, and if it happened to allow incest, that's fine.  I'd hate for the cool concept of royal families to be stifled just to be PC.

As for the bonus/holding back, not marrying your two sibblings to two other nations is really going to hurt you politically.  I'm not sure there is enough to gain to bother addressing it.

there is a difference between holding true to blue blood marraige and incest.... perhaps a fine line, but still a line.

You do realize that it takes generations for inbreeding to become significant?  Yes, if there are already any recessive issues it vastly increases the odds of them showing up, but the overall degredation of the offspring takes time for it to build.

Wha?  Many mideval royal families practically ONLY married cousins.    On top of that, Mideval communities were generally so un-diverse that marrage between any members of the same community was looking at gene pool that is more shallow than almost any set of modern American '1st cousins'.  Let alone second or third cousins.

Incest thing was hilarious in the first Medieval Total War. The generals got some risky traits. Some of those kind of traits were random too, like those that involved an uncle or nephew/niece. In that the inquisitors could use that as evidence of heresy.

Wrong. I have an aunt and uncle (both deceased) who were also first cousins. 4 children, 1 normal, 1 mentally handicapped and 2 blind from birth.

Not good odds and not generations of inbreeding. I've done genealogy on that family line back to the mid-1700s and there was no history of intermarriage.

In any case, I think the question should not be what fits reality, as the game's reality is pliable enough to make just about anything work (preasence of the channeler's hereditary magical ability combats deformity?), and the question should be more along the lines of what would be better from a strategic POV...... my money's on less chance of deformed/wierd/superhuman offspring because hyperpoweful RNGs always leave me feeling just a bit cheated.....