Zake and walimu indicates the plural. For singular it would have been yake and mwalimu
So is kaka one of the 'people' nouns that doesn't go in the m/wa class? Is 'kaka wake' not correct?
All close family members are N class. Kaka wake is not correct. Adjectives agree as if they were M/WA, but possessives use y/z to show plurality.