little sister
kid sister AmE informal

I couldn't even get it up with her the first time because she reminded me of my kid sister.

In her teens she made herself known as a kid sister.

My beloved kid sister, we had such good times together.

He looked at her like a niece or a kid sister.

Except for the kid sister, none of it surprised me.

"I thought she was like your kid sister or something," he shouted.

It's a lot better than if he got involved with the kid sister.

I doubted Jeremy still saw her as a kid sister.

You got your life before you yet, little kid sister.

Aaron was the subject of the article, not his kid sister, Anna.