This was always an issue in Rome. People were afraid their heirs would turn out to secretly be wannabe dictators, and you couldn’t do anything about it since you were dead. How would you go about making sure your heir was as close to your vision as possible, both outwardly and in their desires should they be emperor?
I forget which king it was (I’m sure someone here will tell me) but his solution was to divide his kingdom among his two heirs.
So the idea was that one heir would do the dividing and the other heir would then pick which kingdom they wanted.
This is a great solution to making sure people share a cookie / snack / etc fairly. The divider has an incentive to keep things as fair as possible.
I think this ended in civil war though, so your mileage may vary