WHAT DOES IT REALLY MEAN???
There were the blue-bloods of Ancient Times which extended into European Times. . They actually did have blue blood, and it was not hemoglobin based but copper based. They were semi-human. There are still to this day, some animal species in South America that have copper based blood systems. There was a problem with hemophilia, and not because of intermarrying. The problem was that they started to marry outside of the copper based blood system. Hemoglobin and copper systems don't mix. That's where the laws against marrying commoners originated.
Red Haired Mummies of Egypt