Who is Chris closest to in his family? How do we know?

Carine is Chris’s younger sister, with whom he is extremely close. Carine looks a lot like Chris, and is also energetic, self-assured, and a high-achiever, but unlike Chris is very gregarious, forgiving of people’s faults, and happily fits into capitalist society. Carine is also the only person Chris coresponds with on his journey.