Why would the population of royal families (of England as well as other countries) not qualify for the Hardy-Weinberg principle?

Hardy-Weinberg Principle

A principle that describes the genetic equilibrium within a population, stating that allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary influences.

Royal Families

Hereditary ruling dynasties characterized by a succession of sovereigns from the same family, often maintaining political power through generations.