This is one of my history essays, which touch on a common German term used.....Kaiser.
In simple definition....Kaiser translates purely to 'emperor'.
There is a long and drawn out process which connects the Roman empire, Caesar (the original emperor) and Germany.
Kaiser, at least in the modern sense, relates to the Prussian and Hapsburg Empires (Germany and Austria).
For most of Prussian history.....the term emperor is used....at least from the late 900-era to 1806....as most saw their reign as simply a continuation of the Roman Empire connection to Prussia. It's not until 1871, when Kaiser Wilhelm I assumes the title. Seventeen years will pass, and Wilhelm I will pass on......his son....Fredrich (the 3rd).....will pass on in a hundred days, thus bringing the third and final Kaiser (Wilhelm II) to the top.
For Austria.....the terms start to being used around 1804 with Franz I. Four of the Hapsburg Empire will use the term, with Karl I being the last one.
What remains of the Kaiser family today? The Prince of Prussia is Georg Fredrich, and has the title to show. But these days, he's a business analyst and has little time for the 'profession'.
If you stand around Germans and the term 'Kaiser' gets brought up....it's usually a trivia game or a quiz show. Most will be able to identify the last Kaiser (Wilhelm II) but rarely go past that point to know that there were only three of them in Prussian history.
Most Germans would also let you know that royalty all costs money and it's a thing that you don't need. Oddly, these are the same folks who beg for funding to pay for the upkeep of their local castle, palace, or fortress from the state government tax pot, and go all weepy-eyed when Queen Elizabeth shows up. These ancient relics of an era long-gone.....are the corner-stone to tourism in most German regions today. And oddly enough, there are probably more statues in Germany existing today of Wilhelm I or Wilhelm II.....than any other German figure in history.