Roald Dahl's eldest sibling was his sister, Astri. In his memoir "Boy," Dahl refers to Astri as "ancient" because she was much older than he was and had already passed away by the time he wrote the book. He does not mention her name in the book. As for Dahl's statement that "a person is a fool to become a writer," it seems to have been a somewhat tongue-in-cheek remark. Dahl was known for his sense of humor and his tendency to be self-deprecating. It's possible that he made this comment to downplay the difficulty and challenges that come with being a writer, or to playfully poke fun at the often precarious nature of a writing career. It's also possible that he simply meant that writing is a difficult and uncertain profession, and that one must be somewhat foolish to choose it as a career