When you two brothers fight, Mommy's very sad.         

你们两兄弟打架时，妈妈很伤心。

WHen my son is sick, Mom's heartbroken.                         

当我儿子生病时，妈妈的心都碎了。

When my girl cries, Mom feels so bad.                               

当我女儿哭时，妈妈觉得很难过。

Don't be sad.                                                                      

不要难过。

Don't cry.

别哭。

You need to comfort your friend when he's/she's sad.

当你的朋友很难过时，你必须去安慰他/她。