He's my brother.

 Who's that boy?

 Yes, she is.

 Is she your mother?

 No, he isn't. He's my teacher.

 Is he your father?

Amy：Who's that  (bay   boy)?

Chen Jie: He's  (me  my) brother.

Amy: Is she  (you   your) mother?

Chen Jie: Yes ,  (She   she ) is.

Amy: Is he  (you   your) father?

Chen Jie: No, he isn't.  (he's   He's ) my teacher!