I am a foolish and spoiled person, and I have ended up inheriting the position of family head and the fiancé in place of my distinguished older sister. [Bonus content has been added]

My older sister is admirable. She abandoned her status, social position, and home to become a physician in order to save people's lives. Even when invited to serve as a royal physician, she refused and continues to travel about day after day to save as many lives as possible. "You're spoiled and cute, my Mary? You should be able to inherit this house, at least, right?" "...Yes, Sister Luise." I inherit the house in place of my sister. As the first step, I become engaged to the man who was once my sister's fiancé. "I look forward to working with you, little lady." The one gazing at me gently is the man who once loved my sister with passionate eyes. "It's a pleasure to meet you, Lord Lawrence." What was supposed to end as an unrequited first love instead... Now, this man is my fiancé. [Added an afterward story from the parents' perspective] [I'm serializing side stories and stories before and after the main narrative separately. The content is largely the same.] Also published on Everista.