There's also a lot of suspension of disbelief involved with the lack of a succession/dynasty system. Like was mentioned in another thread about how the lack of lore detracts from the overall immersion into the game, the same goes here with the lack of inheritance. So I've killed the Tarthian leader in my borders, and she dies, but what stops her sons and daughters from taking the kingdom and running it for themselves? They're Channellers too, and should be Sovereigns in their own right. Whenever I make children in this game, they turn out to be vastly more powerful than my Sovereign, with greater potentials, strengths, etc. They could probably do a better job at leading and expanding the kingdom/empire than I could, so why do they disband the settlements and return to the wilds if I croak?

if it was large empire with more than 1 child surviving the empire could split in pieces as new factions