Firstly, I would like to say the Kingdom better pay the maids and knights of the Royal Siblings with stellar sum pay, because if they can live with those kinds of stupidity for 10 years without a meltdown they're Saints.
Second, this is a first. Usually the plot is "He/she is not worthy of my sibling!", this one is "My brother is not worthy of my future sister-in-law." Nice, and I can see the train wreck that fills future chapters.