The Prince of Wales and his younger sister, the Princess Royal, are only two years apart in age and have shared a close relationship from an early age.
Prince Charles and Princess Anne were just toddlers when their mother, the Queen, ascended the throne and relied on one another for company when their parents were away on royal tours and engagements.
The pair have also been present for key moments in one another's lives, such as Charles' investiture as the Prince of Wales in 1969, Anne's participation in the 1976 Olympics in Montreal and their respective weddings.
Take a look at the sweetest photos of the royal siblings from childhood to now.
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Charles and Anne were pictured playing together outside a miniature house in the grounds of Windsor Castle in 1954.