The origin of the royal headpiece, a crown, came about quite literally from the crown of people’s skulls developing an upward growth that was essentially a jagged, circular protuberance from their heads. People worshiped the individuals with these strange growths, thinking it was a special quality bestowed on them by the God or Gods they believed in. Eventually, these royal crown-havers began decorating their bony crowns with paint and other adornments to be visible at a distance. As generations went by, the crowns receded, so artificial crowns were fashioned for their heirs to wear to signify that they are from the lineage of the true crown.
When a naturally-crowned king married a common woman, his natural crown would be mimicked with jewels and gold and adorn the head of his queen. However, when children were born, they often never grew the anticipated natural crowns, as we know now it is a recessive trait. This is where the custom of royalty marrying royalty came into play during the middle centuries. Doing so allowed for truly royal lineage to continue to be passed, and a greater chance for their offspring to have these natural symbols of supposed supremacy. Of course, copulating within royal families led rapidly to inbreeding, which led to birth defects and genetic illnesses. All of this resulted in the rapid decline in naturally-crowned individuals. The legacy lives on, however, in the monarchs of today who adorn expensive crowns upon their heads, and still believe themselves to be of a chosen lineage.
This belief, of course, is erroneous at best, and seen by many as despicable.