Notes69 解析双重所有格)

Are Sunny and Patty Emma and my classmates?
(Sunny和Patty 是Emma和我的同學嗎？)

Yes, they are(前二者). They're your (後二者的)classmates.
No, they aren't. They aren't your classmates. They're your friends.

說明:
所有Be動詞句型: 主+動+補。
Sunny and Patty (主詞)前二者
Emma and my classmates(補語)後二者。
雙重所有格用法A and  B's  是指A與B共同擁有的，僅後者用所有格就可以。
反之，例如 Emma's and Molly's teachers 表示兩人各
別不同的老師。

以現況例 Jimmy is Patty and Molly's teacher.
(Jimmy 是Patty  及Molly  的老師)。而老師僅Jimmy一人而已。
Patty's and Molly's mothers are nice. 指両人的媽媽不同人，有二位用are.

再回頭看以前的句子

Is Jimmy Justin's classmate?
ㄧ〉 Is jimmy Patty and Justin's classmate?
ㄧ〉Is Jimmy Patty and  my  classmate?

  No, she's not. She's not his classmate. She's his schoolmate.