While your math is sound, and stable timelines are great, not all Lucian Kings would be the child of the previous King. In English history there were several kings who were brothers and who all died within a few years of each other, and when the last of them died they were succeeded by an uncle. A King dying early and being replaced by a sibling or other close relative would certainly have happened many times, and especially so if one wants to keep to the iffy canonical 2k years.
Hhmmm. That’s true.
But even with that I would think 2k is cutting it kinda close.
I mean, it certainly happened within the Lucis Cealum line, but not as often as one might think.
For the Lucis Cealums we can’t forget the sisters. I think, even if all brothers were to die and there would be an uncle still alive, it would still be the sister who inherits. Even if this is not how the humans would have done it, Bahamut will make sure of this.
Gender doesn’t really matter to an Astral.
This is why in my list of all 113 rulers, Crepera is the first ruling queen and the 17th monarch. In canon her father and brother died in a daemon attack. I don’t know if there was an uncle.
But there are also a few headcanons playing into my reasoning of a fairely straight line of rulers.
One of them is that the members of the royal family don’t get that old. 60 at most. Because the crystal is stealing their lifeforce to sustain itself. Power has a price and this is part of what the Lucis Caelums have to pay.
Another is, like I said, Bahamut indirectly interfering. It’s him who approves of the new rulers and he likes to keep it parent to child when possible.
Lastly is that the Lucis Caelum line has slowly been dieing out, only producing one child per generation for some time now. To keep the count of important players as low as possible when the prophecy happens. Meaning that when Bahamut promised Ardyn the line would end with the Chosen King, he wouldn’t have to chase down various uncles, aunts and cousins.
