Egyptian Pharaohs were not "ordained" or empowered by their gods, they were considered descendants of their gods and as gods themselves.
I'm not sure how the Greek Ptolemies managed to take over and spin that one, because there were dynasties before them and Alexander left Egypt to the first Ptolemy (again, Alexander gave away something that wasn't his to give, but he got away with that, too) so the Egyptians had to know that Ptolemy wasn't a descendant of their gods, but they bought it anyway.
And Robert, you are quite right that this whole discussion would make a good dissertation.
And it is true that the Vanderbilts, and the Astors married into royalty. And Jackie Kennedy's aunt married into Russian royalty the Radziwills. After we colonists gave Hanoverian George III the big push out, about 100 years later, we began to try to marry our daughters into a title. Any title would do.
But aside from monetary royalty and that includes big industry and Hollywood, we have no "royalty". We just treat some people that way.