Touya should have suspected something like this since the motto of Lihnea Kingdom is: "Ain't No Lovin' Like Cousin Lovin'."
Recall several chapters ago when it was said that the prime minister was cousins with the bad queen, and even in this one he talked about "our family." Do you want your dynasty to be like the Hapsburgs? Because this is how you get a dynasty like the Hapsburgs.