Ahab asks this question to express surprise. Alternate translation: "I am surprised that he is still alive!" (See: [[rc://en/ta/man/translate/figs-rquestion]])
"My brother" here is a metaphor for somebody who is a good friend. Alternate translation: "He is like a brother to me" or "He is like family" (See: [[rc://en/ta/man/translate/figs-metaphor]])