The Queen' s oldest granddaughter, Zara Tindall, isn't a princess due to a royal tradition - even though both Beatrice and Eugenie are princesses. Zara's cousins, Prince William and Prince Harry, both hold the royal rank, but her brother, Peter Phillips, doesn't - and it's all down to their parents.
Royal Family tradition dictates that only the father passes on his official title, so the children of Prince Andrew, Prince Charles, and Prince Edward all automatically became princes or princesses. However, because Peter and Zara are the children of Princess Anne they didn't receive the HRH status.
