Charlemagne lived 1300 years ago.
Allowing for three or so generations each century and the fact that each of us has two parents that gives each of us 2 to the power of 40 direct ancestors ... 1,099,511,627,776. (The current population of the planet is about 8,100,000,000.) Distant individual ancestors will almost certainly appear multiple times in our family tree.
In addition, Charlemagne had at least 20 children.
And random events such as the black death decimated the populations of nations on more than one occasion.
It is statistically inconceivable that any of us does not have Charlemagne in our family tree ...