我姐姐有三个已成年的孩子。

My sister has three ___grown-___up children.

作为一个成年人，你必须自己做决定。

As a ___grown-___up, you have to make your own decisions.

别像个小孩子一样——试着更成熟些！

Stop acting like a child - try to be more ___grown-___up!