妹を

younger sister

→ 妹
phrase Uncommon #9,499
younger sister 妹 means “younger sister”; を marks it as the direct object of the verb, so the phrase often translates as “younger sister” or “his/her younger sister,” depending on context.
JA: 妹を駅まで迎えに行きます。
EN: I’m going to pick up my younger sister at the station.

妹をパーティーに連れて行きます。

I’m taking my younger sister to the party.

ピザを食べている間に、彼は妹をイライラさせていた。

While he was eating pizza, he was annoying his younger sister.

ジェーンと彼女の双子の妹を区別できますか。

Can you tell Jane and her twin sister apart?

彼は妹を連れて行った。

He took his younger sister with him.

私は彼女と妹を区別できなかった。

I couldn't tell her apart from her younger sister.

彼は母と妹を扶養しなければならない。

He has to support his mother and younger sister.

妹をお願い

Please look after my little sister.

— ロード・オブ・ザ・リング/二つの塔 (2002)

トムは妹を押し入れに閉じ込めた。

Tom locked his younger sister in the closet.

彼は妹を私に紹介した。

He introduced his younger sister to me.

パコ妹を助けて!

Paco, help my little sister!

— ROMA/ローマ (2018)

妹を家に連れて帰らせてくれ

Let me take my sister home.

— RRR (2022)

これは私の妹を撮った写真です。

This is a photo I took of my younger sister.

人の妹をじろじろ見るな

Stop staring at my sister.

— ロード・オブ・ザ・リング/二つの塔 (2002)