The following is a list of Kings and other rulers in our family tree from whom we are direct descendants. The list started small then continued to grow. It shows how the different royal families intermarried and thus were related.
I have read somewhere that King Edward III of England and his consort Philippa of Hainault have around 1400 lines of descent from Charlemagne.
It is also believed Edward III, the most recent on this list, has over 4 million descendants.
A Guardian article claims all present day Europeans (and I suppose by extension most of us of European descent) are descended from Charlemagne.
Another site claims all US presidents are descended from King John of England. Since this page is a few years old Presidents Trump and Biden are not included.
I think it is important to note the title of King varies in location and time. Some Kings in Ireland and Wales were kings of a portion of the country where there were numerous kings at the same time. A high king might be the most prominent king among several, not the only king. Even the title Emperor could have different meanings.
All information is provided for the free use of those engaged in non-commercial genealogical research. Any commercial use is prohibited. Kim Simmonds' Family Genealogy https://kimsimmonds.net/