An elder brother, a younger sister, an elder sister.

一个哥哥，一个妹妹，一个姐姐。

youdao

I have one older sister, one younger sister and one younger brother.

我有一个姐姐、一个妹妹、一个弟弟。

youdao

He had a younger brother, Abbott Lawrence, and a younger sister,Amy.

VOA: special.2010.07.11

You remember they're wandering around the forest without her picking berries. The younger brother, - the second brother, is most concerned about his sister's safety -- so I want you to look at this passage.

你们记得他们在树林中游荡,没有拿他们采摘的果子，小哥哥，也就是二哥哥，是最关心他妹妹安全的-,所以我想让你们看这篇文章。

耶鲁公开课 - 弥尔顿课程节选

Let's say that you're talking to your younger brother and sister.

假设你正在和弟弟妹妹说话。

It's important 课堂 - SpeakingMax英语口语达人

Older sister Rose is a dowdy and dutiful lawyer, younger sister Maggie a beautiful and insecure "wannabe" whose crimes against her sister include stealing her shoes and sleeping with her new boyfriend.

WSJ: Lucinda Rosenfeld, Author of The Pretty One, on Sisters | Word Craft

Growing up, he and his family--his older sister works for Goldman in Hong Kong and his younger sister is a doctor in the U.K.--lived in the sprawling Genting Highlands Resort in the mountains, an hour's drive from Kuala Lumpur.

FORBES: On The Cover/Top Stories

Her elder sister Ejegayehu was an Olympic silver medalist in 2004, while younger sister Genzebe was the 2009 world junior cross country champion and a younger brother Dejene is a promising 800m runner.

CNN: Born to run: Ethiopia's golden girl Dibaba