かぞく
Two words for every relative — and it depends whose

Talking about your own family to someone outside it — the plain, humble set.
ちちは せんせいです
Someone else's family. It's also what you call your own parents to their faces.
ゆきさんの おとうさん
〜にん from Unit 58, including yourself. よにん, not よんにん.
よにん かぞくです

フジさんの おとうさんは?

ちちは ぎんこうで はたらいています。
ふたつの ことば
Japanese keeps two words for every close relative, and picking between them is not about being polite in general — it is about whose family you mean. 🔊 Tap any word to hear it.
Talking to an outsider, you play your own side down and the other person's up. So ちち for your father and おとうさん for theirs. Using おとうさん about your own father to a stranger lifts your own family — the exact thing this pair exists to avoid. At home, though, you call him おとうさん to his face: inside the family there is no outsider to be modest in front of.
どちらを つかう?
In practice the question is always the same: am I talking about my family, or someone else's? The two younger siblings barely change — they just take さん when they belong to somebody else.
The left column is for your own family, talking to someone outside it. The right column is for everyone else's family — and it is also what you call your own parents to their faces. So おとうさん is both “your father” and what you actually say at home; ちち is what you say about him to other people. The younger siblings barely change: おとうと and いもうと just take さん when they belong to someone else.
なんにん かぞく?
Nothing new here — it is 〜にん from Unit 58, with the same irregular ひとり・ふたり・よにん. The count includes you.
The counter is 〜にん from Unit 58, and it counts everyone including you. Asking uses なんにん, exactly as it did there — so this whole pattern is Phase Q furniture with one new noun on the end.
かいわ
Notice how the speaker switches columns mid-conversation: asked about おとうさん, they answer about ちち. That swap is the whole unit in one move.

なんにん かぞく ですか。
How many are there in your family?

よにん かぞく です。
Four of us.

きょうだいが いますか。
Do you have any siblings?

はい、あねが ひとり います。
Yes, I have one older sister.

おとうさんは なんの しごとを していますか。
What does your father do?

ちちは ぎんこうで はたらいています。
My father works at a bank.

おかあさんも はたらいていますか。
Does your mother work too?

いいえ、ははは いま やすんでいます。
No, my mother is resting at the moment.
クイズ
Twelve questions. The English tells you whose family each sentence is about — that, and nothing else, decides the answer.
Question 1 / 12 · 0 correct