So i got a good 4 / 3 / 6 heir as byzantium and its 1358 and somehow this heir is "locked" (i dont know how to say it better) for death - no matter how many times i reload this guy will die and immediately replaced by another new heir, sometimes in february, sometimes in may - but he will die for sure in 1358. Is there some hidden event to kill above average heirs regularly or whats going on with my game?