Randolph According to the family tree my paternal grandfather drew up before he died in 1989, my earliest (known) ancestor is Gilbride, Earl of Angus. This is correctly written as Gille Brigte, considering that Gaelic was the language of the day.
There is very little information on the link between him and the House of Stuart, with which I am also associated. Of course, being able to trace back so far kind of lessens the effect, because it means that I'm most likely related to everyone else in the world.
More info on Gille Brigte on the related link.