Mary and Robert's fathers are brothers.Do you know your parents's birthday?这2个句子有错吗,各错在哪里

Mary and Robert's fathers are brothers.Do you know your parents's birthday?这2个句子有错吗,各错在哪里
Mary and Robert's fathers are brothers.Do you know your parents's birthday?
这2个句子有错吗,各错在哪里

Mary and Robert's fathers are brothers.Do you know your parents's birthday?这2个句子有错吗,各错在哪里
mary and robert's father 是一个人 指他们有同一个爸爸 要改成 mary's and robert's father 才对
parents's 应改成 parents' 复数名词直接在后加'

Mary改Mary's
parents's改parents'