Fascinating stuff. William I The Conqueror was the first King that I found in my line, and from there to Charlemagne to Flavius Theodosius I(that's not the end, but the line and dates after are 'iffy'. Many Emperors, Kings, and Queens from all over Euope, Asia, Middle East, and even a few Saints lol.
Maybe it's really not that rare, but two of my other lines don't go far at all.
It's all academic, but it is interesting.
So glad I joined Ancestry.com, otherwise I would never have known this.