When a country has no heir but a royal marriage with a country with more prestige, three things can happen on ruler death:
1. A noble from the other country gets the throne (same dynasty).
2. A personal union is formed.
3. The country gets inherited.
What determines what will happen? I already tried to lower their prestige below zero and increase relation, but the displayed message, about what will happen when the ruler dies, did not change.
Is the displayed message reliable at all? I read it is not, e.g. when a ruler in a personal union dies there is always a chance to inherit regardless what the message states.