妹と

with a younger sister

→ 妹
phrase Uncommon #12,631
with a younger sister 妹 means “younger sister.” と commonly means “with” here, but its role can vary depending on the verb.
JA: 妹と映画を見に行った。
EN: I went to see a movie with my younger sister.

彼は私の妹と婚約している。

He is engaged to my younger sister.

トムはメアリーの妹と婚約している。

Tom is engaged to Mary's younger sister.

俺、姉貴のボーイフレンドの妹と付き合ってるんだ。

I'm dating my older sister's boyfriend's younger sister.

妹と動物園に行ってきたんだ。

I went to the zoo with my little sister.

誰を紹介するかで私は妹と口論となった。

I got into an argument with my younger sister over whom to introduce.

今ちょうど、妹とお昼を食べてるとこ。

I’m having lunch with my younger sister right now.

妹と私は交換で部屋を掃除します。

My sister and I take turns cleaning the room.

彼女はその時、妹と遊んでいました。

She was playing with her younger sister at that time.

以前はよく妹とその公園で遊んだものだ。

I used to often play in that park with my younger sister.