“...For example, Queen Victoria, a major proponent of pure blood lines, married her cousin Albert, and the two had nine children who then passed hemophilia”
Correct. One defective X chromosome is sufficient to pass the disease to a son, or make a daughter a carrier.
Yes a mutation. I don’t think her parents carried it,unless her father was not her biological father.
Hemophilia is a sex-linked trait carried on the X chromosome making it dominant in males and recessive in females. Baldness and color blindness are also sex-linked.