How does the game determine what kingdoms a prepared invasion will target? I want to prepare an invasion on either West Francia or Aquitane, but I haven't been able to do it so far. I saved just before declaring the invasion in case there was an issue like this, but despite reloading and waiting for different conditions I remain unable to target either kingdom. Each is the primary title of its respective holder, but declaring on the King of Aquitaine gives me an invasion for Aragon, despite that king only controlling one duchy in Aragon. Similarly, an invasion of the King of West Francia targets Swabia (a kingdom-tier title in HIP, which I am using), even though his demense is entirely within West Francia and the Swabian title hasn't even been created.
Under what conditions will I be able to target those two kingdoms? I have been holding off on creating the Kingdom of Norway because I want to declare an invasion before my realm is too large.