old soul

One who has a deeper understanding or appreciation of things than would be expected of their age. Marie has always been quite the old soul. Even in high school, she never seemed to fit with other teenagers, preferring classical music and nature walks over parties and football games. A: "Alex asked me this morning if a person could live in our hearts after they pass away." B: "Your five-year-old asked you that? I'm telling you, that kid is an old soul."