I think there is some confusion here over where one is in the line of succession-i.e. whether the line of succession should follow the male line or not-and whether one is "royal". Some people want the line of succession to ensure that a female child born to Prince William and Catherine would have the first place behind William in the line of succession. That is not the same thing as being, "royal". Any child born to Prince William and Catherine would be a member of the royal family.
rawsilk
There is no confusion.
The term
royal family is informal and has no legal definition. The term
royal is specified by the letters patent issued by King George V. According to the letters patent, children of a monarch, grandchildren of a monarch via sons, and the oldest son of the heir to the Prince of Wales are
automatically royal. No one else is royal unless the monarch specifically issues new
letters patent.
For instance King George VI issued
letters patent in October 1948 that said that any children born to Princess Elizabeth would be royal. He did that because he was already 53 years old and he did not expect to have a son. But Charles and Anne were grandchildren of a daughter and did not automatically become royal.
Now Charles and Anne would have become royal automatically as soon as their grandfather died. In the same way Prince William's daughter would become royal automatically as soon as Queen Elizabeth II dies. But we assume that, like Charles and Anne, she will be made royal by the issuing of "letters patent".
BACKSTORY
In 1917, there were roughly 50 British royals including princesses who were using the title because they were married to British princes. They were royal because of
letters patent issued by Queen Victoria which confirmed the traditional German rules for determining who was royal. Her grandson was both concerned about the number of royals, and the fact that at least 10 British Royals were Germans who grew up in that country and were now fighting a war with the UK. He severely restricted the relatives of the monarch who would become automatically royal.
It should be noted that Ernst August V, Prince of Hanover, Duke of Brunswick(age 57) and the estranged husband of Princess of Caroline still claims to be a Prince of Great Britain and Ireland. Just before WWI his father was granted made a British Prince (as a baby). In issuing the titles deprivation act, the families British Dukedome was revoked but their style as British princes was not formally addressed. The British government does not recognize him as a prince however, but insists that he re-apply for this title.
Today, The British government believes there are only 15 people who are
royal because of being born to the royal blood. In addition there are 5 women who assume the style of their husband, and Prince Phillip. The ones born are The Queen, four of her cousins, her four children, and six of her eight grandchildren. There are 3 wives to her male cousins, 2 wives of her sons, plus Prince Phillip. Prince Phillip does not take the style of his wife, but was made a Prince by his wife by issuing of letters patent during her fifth year as monarch.
Well, technically speaking, Elizabeth II did not create "the Duke of York", of course! The title had been around for centuries. She simply granted it to Andrew.
In the language of titles you either inherit your title from your father or it is
created. If it is a traditional title that is available again then it is
re-created. The Duke of York title is famous for the seeming inability to pass it down from father to son. It is constantly being re-created. In the case of Prince Andrew he has no sons to inherit his title. When he dies the title of DOY will be re-created in someone new (probably the second son of Prince William).