All Arabian horses go back to the Bedouins. Al Khamsa, meaning " the five" are supposedly horses who trace back to prophet Mohammed's five war mares.
My honest opinion on that? No Arabian is purer than pure. There have been arguments over arguments on the internet about straight this, straight that, Al Khamsa, Blue List, Asil, whatever....the World Arabian Horse Association came up with a definition of the purebred Arabian and that's it. Everything else is just marketing.
They all go back to the horses imported from the desert, in the desert nothing was written down, just word of mouth.
Sorry if I busted anybody's bubble......