Anybody interested royal families—real or fictional—has probably heard the term "the heir and the spare." The term, which is meant to be humorous, pokes fun at royal and noble families needing to have at least two children—one to succeed to a title (or the actual throne) and another to guarantee the family line will continue should anything happen to the first born. According to royal historian and Battle of Brothers author Robert Lacey, this is how Prince William and Prince Harry were treated within the royal family.
Because Prince William is the oldest child of Prince Charles, he's second in line to the throne. His younger and only sibling, Prince Harry, was third in line to the throne until Prince William had children. After Prince George, Princess Charlotte and Prince Louis were born, Prince Harry was bumped down to sixth line. With each of Prince William's children, Prince Harry became a less essential member of the royal family.
"I would say William has been more kindly treated than Harry has been, but that has always been the fate of the spare," Lacey said, according to Express. "Harry follows, sadly, in the tradition of Princess Margaret or Prince Andrew as number twos in the system, who are treated harshly by the logic of the royal system which actually favors the main bloodline."
"When they are born and are young and children, the spare is always so close to the centre of things and it is their destiny, through life, to be pushed ever outwards," he explained. "In technical terms, of course, they go down the line of succession. From Harry being right next to William in the succession, he is down to six, seven, eight or so."
Even though Prince Harry has stepped down from his official role within the royal family, he remains sixth in line to the throne.