كَمْ رَجُلًا أَخُوكَ؟
كَمْ: interrogative, fixed on sukūn; the source classifies it as a nominative-position topic.
رَجُلًا: accusative tamyīz.
أَخُوكَ: the “six nouns” pattern: akhū is nominative with wāw, and ka is the genitive attached pronoun.
This somewhat artificial question serves as a syntactic illustration, not a model of ordinary conversation.