Okay I did a bit of digging and found some things out.
This is from chapter 44 of the Warbreaker annotation
It is possible for a Returned to have a child. Vo, the First Returned, did it. The God King isn't special in that he can do it; any of the Returned could, but it requires some special knowledge that—I'm afraid—I'll have to keep secret until the sequel. Suffice it to say that the priests know how it is done.
The problem is, they aren't always able to get this to work. Sometimes, they have to do what Siri guessed—replace the God King with an infant Returned. Infant Returns happen very infrequently. It's more rare than an adult Returning, so there is something sound to the Hallandren reasoning that you have to do something heroic in order to Return. (That's not true, but it is more sound a doctrine than Siri thinks it is.)
This is from a Twitter interview in July of 2009
Graendal: A question that's been on my mind for a while. If Returned can't have children, how are Siri and Vivenna descended from one?
Excellent question. One I have to RAFO. When I was writing WRBRKR, I was planning on two books.
I seeded two questions to be answered in the next book. One was the origin of the royal family.
The second was how Vasher was able to survive while hiding his divine Breath. I will answer these questions.
Eventually. (It has to do with restoring Breath and life to the child while still in the womb.).
This clears up the Returned having children, their is something odd going on, a secret, but it is clearly possible.
Warbreaker Chapter 32
"The First Returned was born during this time," Hoid said, sprinkling a handful of silver glitter into the air before him. "Aboard a ship that was sailing the coast. Returned can now be found in all parts of the world, but the first one—the man whom you call Vo, but we name only by his title—was born here, in the waters of this very bay. He declared the Five Visions. He died a week later.
Okay I was right, Vo did die after a week, but I'm thinking they already had Breath, because then he wouldn't have Returned looking like the other Returned that were to follow. We have no idea how different the other type of Returning is from the one we know.
And now I have something of a timeline, from Chapter 32 as well.
The glitter ran out, and Hoid began to drop a powdery brown dirt from his other hand as he reached into another pocket. "Now, you may wonder why I must travel back so far. Should I not speak of the Manywar, of the shattering of kingdoms, of the Five Scholars, of Kalad the Usurper and his phantom army, which some say still hides in these jungles, waiting?
"Those are the events we focus upon, the ones men know the best. To speak only of them, however, is to ignore the history of three hundred years that led up to them. Would there have been a Manywar without knowledge of the Returned? It was a Returned, after all, who predicted the war and prompted Strifelover to attack the kingdoms across the mountains."
So this says that Vo Returned 300 years before the Era of the Manywar
"You know, perhaps, that the royal family was growing increasingly interested in the process by which Breath could be used to bring objects to life. Awakening, it was then first being called. It was a fresh and poorly understood art, then. It still is, in many ways. The workings of the souls of men—their power to animate ordinary objects and the dead to life—is something discovered barely four centuries ago. A short time, by the accounting of gods."
To put this in context it was talking about the royal family during the time of the Manywar. So when those two quotes are put together, a bit of a timeline can be put together. According to my theory, first Endowment arrived on Nalthis, and probably not too long after, Vo Returned. 300 years later came the discoveyr of Awakening, the 5 Scholars, and the Manywar. Around 400 years after that comes the events of Warbreaker. I was a little off on the dates so I'll edit the first post soon, but so far, nothing contradicts the basic precepts of my theory.
Back on topic, what if Endowment created people on Nalthis (with Breath, as Deus Ex Biotica mentioned), then went on vacation to another Cosmere planet, possibly one we haven't even heard of (thus no Returned, but Breath continued working as usual), then came back a few centuries ago (as Windrunner described).
Possible, but personally, I doubt it. I don't see any possible motivation for leaving Nalthis. The only Shard that we know for sure has left it's planet is Odium, who went to murder Aona and Skai. I can't see a Shard with an intent that means giving, going to kill anyone else. Maybe she was escaping Odium, but I don't see him leaving the inhabitants of Nalthis unharmed. I don't know that the Returning would stop if Endowment left, Preservation had no mind and it still was on auto-pilot snapping people. Also Vo probably wouldn't be called the First Returned, because there would be myths of others from before Endowment left.
Edited by Windrunner, 25 November 2011 - 01:25 PM.