改病句，帮帮忙！谢谢

Tom's and Tim's -- Tom and Tim's

注释：
Tom's and Tim's 表示“两人分别拥有的，不共有”
Tom and Tim's 表示“两人共同拥有的”
由于两人是双胞胎，所以生日应该是同一天。

Today is Tom and Tim's birthday. They are twins .

Today is Tom and Tim's birthday. They're twins