Weren’t both William and Harry Princes of Wales until William married? At that point William was given the new title Duke of Cambridge. When Harry gets married, he will probably be given another title. I remember reading that both the boys were simply called “Wales” at school, and Harry in the army.
Nope. Charles is the only Prince of Wales as of now. Once he becomes King (ugh), he should bestow the title on William, as he is next in line for the throne. Charles was created Prince of Wales in 1958, although his investiture did not take place until his mother crowned him in 1969. In 1970, he took his seat in the House of Lords.