If I Offer a Poisonous Plan, Won't You Rebel?

Lu Yuanxiu traveled through the fantasy world and became the heir apparent of the Duke's mansion. I originally thought that the Duke's mansion was full of loyal people, but it turned out that something was wrong with the whole family. Big brother: "Father, the girl I'm interested in has a good background. She's your Majesty's ninth princess. I think I can forcefully kidnap her back to the house, make her cook raw rice, and then perform a cruel trick on your majesty. The princess will naturally get married." Father: "No, no, no. Once the princess gets married, Yuan Xiu can no longer take concubines. My father thought that he could create an accident and make the Ninth Princess disappear, and then abduct her without anyone noticing, and imprison her in the house for the rest of her life." Mother: "In my opinion, it's better not to go to so much trouble. I suggest starting the dragon-slaying plan to destroy the royal family. By then, all the princesses will be distant cultivators and upright." Just when Lu Yuanxiu was dumbfounded, the system woke up. To fight violence with violence, if you want to defeat a madman, you must be crazier than him. So Lu Yuanxiu came up with a poisonous plan. "Father, my son suggested creating a plague, and then using the plague army to rebel and attack surrounding countries. This would kill two birds with one stone." As soon as these words came out, the whole place was silent. "We won't do this anymore. I just want to be the emperor. I don't want to be remembered in the history books for thousands of years -"