Unfortunately and family tree that many generations back in Geni.com or any other source is highly questionable and lacking proof! But it is estimated that over 100 million people living today may be related to Charlemagne due to the frequency of close relative marriages among royalty for many many generations. Ghengis Khan is also a common ancestor of millions.
Douglas, you are completely correct. No one on Geni can state with 100 percent accuracy that the Geni relationship calculator is correct. It is only as correct as the information uploaded is correct. And, as I have discovered, even when many of my lines are correct and proven, sometimes people make changes to my that aren't correct. Or, I will discover new information and when many of my lines are curated and locked for protection purposes, it is another project to update my lines. However, I highly recommend having a curator lock your proven lines, even if it does take extra time.
Great to meet you, 18th cousin! It is good to hear from someone so enthusiatic about Genealogy, their personal ancestors, and Geni.com. My departed Grandmother Myra Jacobs Sheldon and her cousin professional Geneologist Rev Frank Kennth Barta passed along incredibly accurate geneology notes with bibliography to my Aunt Jane Sheldon Sharpe. Fortunately Rev Barta's meticulous research matches well with Geni.com and many of our royal and historical ancestor profiles are already locked by curators or are being updated by equally meticulous authors. Many Counts von Rantzau, Princes von Schwarzburg-Rudolstadt, and the Wettin (Windsors) Royalty are ancestors and cousins are just a few generations back on my tree with Hapsburgs, Danish Kings such as King Christian III and Queen Isabella and King Ferdinand of Spain being well documented and locked ancestor profiles about a dozen generations back. I have traced Ken Barta's notes of ancestors back to Charlemage matching exactly with Geni.com! Thanks for the suggestion of requesting curators to lock profiles which appear to be most factual.