they themselves和their own的用法与区别

如题

这么说吧 有一题说Parents seem to forget how( )felt when they were young.中选项有“their own”和“they themselves”答案是选“they themselves”，如你所说“their own”用作定语，此题当然不可填“their own”，但是我想问“they themselves”是什么结构，什么用法，谢谢

they翻译成他们,在句子中做主语.例句:They are buying vegetables.
themselves翻译成他们自己,在句子中做补语.例句:They learn Chinese by themselves.
their own翻译成他们自己的,在句子中做定语.例句:These are their own works.

呵呵,可以是可以，不过你后面要加个'

比如：some people have pools of themselves' in their yards