Mary and Robert's fathers are brothers.Do you know your parents's birthday?

问题描述:

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'