My Cat Told Me the Beggar is the Lost King

My stepsister refused to marry a beggar. So my family forced me to take her place. They laughed. I smiled. A stray cat had just whispered his secret: he was the missing king. He had lost his memory, but he swore to protect me. Now my sister wants the man she threw away. Too late. She gave me her beggar. What will she do when she has to bow to his queen?