Japanese Phrase for Asking About Family Size: "何人家族ですか？"

"何人家族ですか？" (Nan-nin kazoku desu ka?) means "How many people are in your family?" and is a basic way to ask about someone's family size in Japanese. It's commonly used in casual conversation among children. Typical replies use "〜人家族です" (~nin kazoku desu), as in "三人家族です" (San-nin kazoku desu, There are three people in my family).