Perhaps you can answer this other question for me as well. I've been meaning to ask it for a while and this seems as good a place as any. How do historians generally feel about Heshemite claims of descent from Mohammed? How do other Muslims feel about these claims? If these claims are serious, why have they never tried to set themselves up as Caliphs?
Well I'm neither Muslim nor Jordanian, but I can tell you this, there are somewhat above 100 000 people whose claim to be descendent of Muhammed are general accepted by Muslims, so while it's both likely true and it have some symbolic meaning, I doubt it really have that much political effect.
An interesting myth I have heard, are because of the effect of dynastic marriage in Europe, and one of Muhammed descendents married a Christian prince, is that all royals in Europe are in fact descendent of Muhammed.