My old grandparents stay at the elders'house. They are very happy.
The elders'house = 老人院是home 不是house而且前面还有一个old呢。。elder 是 old 的变形the elders's home = the home of the elders ，中文可翻译为：老年之家/养老院。那括号里应该填什么呢？不好意思，我理解错误。括号里填写“people's"