nostr:npub1yhj4ua6580h3w0kucwwrtwl4uv9pg7m2drxzplq5x3364jczp36s4h3h3t my chatgpt says 0 which is technically a valid answer, since it doesn't say whether sally and the brothers are half or full siblings, but the reasoning chatgpt made doesn't make sense:

Sally has 0 sisters. Each brother has Sally and another sister, making it seem like there are 2 sisters, but they're counting Sally herself.