Within the Royal Family there are several specific rules which explain who is entitled to hold a prince or princess title. These date from Letters Patent by King George V in 1917, where he wrote that all the children of the sovereign, the male-line grandchildren and the Prince of Wales’s eldest son were all allowed to hold a princely style.
Several areas of precedence changed in 2012 when Queen Elizabeth issued a new Letters Patent, which changed the Law of Succession to absolute primogeniture - meaning that all the children of the Prince and Princess of Wales were titled as princes or princesses and any younger brother could no longer overtake his sister in the line of succession.This would explain why the late Queen's eldest granddaughter, Zara Tindall, does not have a royal title of her own - but the monarch did reportedly offer to change the rules.
Princess Anne's daughter is not a male-line descendant of the late Queen, and, as a result, Zara was not entitled to be styled as a Princess of the United Kingdom.
It was reported that the monarch offered to break the rules and give both Peter and Zara official titles of their own. However, Princess Anne refused the gesture as she wanted her children to have as normal of a life as possible.
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