Fix Your Sister's Immortality

Being reborn as the young master of a prominent family, with a powerful father who's a prominent figure in the realm, and a cute, aloof little sister—it was the perfect start. Until one day, I discovered that my sister had a fiancé who was dumped before I transmigrated. This former fiancé was the eldest son of a declining family, with no talent and his family in ruin. He left after saying, "Don't underestimate a young man in poverty," and went off to wander the world. At the same time, there was a house servant in our family who had always been silly and slow. But just before I transmigrated, he suddenly became sharp and intelligent. He then offended the steward and was kicked out. And then there's the young master of the neighboring family, whom I, in my previous life, had beaten into a vegetative state. Apparently, he woke up a few days ago, and he's completely changed. It feels like I'm in over my head. I just want to know what to do. Online help needed, ASAP!