Getting an heir from a different house.

[Nightwing]

So, how does this actually happen? I'm not talking about when a king dies childless and a noble from house whatever succeeds, I'm talking about when you actually get an heir, but he's not from your dynasty. Not that it's a problem-quite refreshing for me actually-but I dunno what actually causes it.

 

[Xara]

It's an event that can happen when a nation has 4+ royal marriages and one of them is to a nation without an heir. It inserts their dynasty as the next-in-line with a spawned child.

 

[sgt.stickybomb]

its random really