Don't be so mean to your little brother.

对你的小弟弟不要如此刻薄。

《新英汉大辞典》

Look after your little brother.

照看你的弟弟。

youdao

Can your little brother count from 1 to 100?

你弟弟能从1数到100吗？

youdao

Let's say your little brother is just learning how to tie his shoes.

假设你的弟弟正在学习怎么系鞋带。

Don't 课堂 - SpeakingMax英语口语达人

Your young brother or sister, or my little children, can draw pictures of family members that barely look like family members.

你的弟弟妹妹或者我的小宝贝们,可以画一些看起来,仅仅有点像家庭成员的画

耶鲁公开课 - 死亡课程节选

And you go and live with your father and your little brother, and you visit your mother at weekends.

NEWYORKER: Homework

How do you feel when you lose because your little brother made Yellow Toad accidentally hop on your polka-dotted cranium?

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And you have to move from your family house to a flat, and your new bedroom is tiny and you have to share it with your little brother, who drives you mad.

NEWYORKER: Homework