A hearer knows Zayd and his brother separately but not their identity. Which assertion is informative?

Indefiniteness, Specification and Definiteness of the Predicate

• زَيْدٌ كَاتِبٌ
• أَخُوكَ عَالِمٌ
• زَيْدٌ رَجُلٌ
• زَيْدٌ أَخُوكَ