The youngster was beaming in her birthday photo - but did you notice the hidden detail?

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Queen Elizabeth II and Princess Charlotte

Pippa Middleton split template with Prince William, Kate Middleton, George, Charlotte and Louis

Kate Middleton split layout with Prince George, Princess Charlotte, Prince Louis

Kate Middleton and Princess Diana

Prince George of Wales, Prince William, Prince of Wales, Prince Louis of Wales, Princess Charlotte of Wales and Catherine, Princess of Wales during Trooping the Colour on June 15

Prince William and Prince George

Kate Middleton with Prince George, Charlotte and Louis on royal balcony

Children in nursery singing nursery rhymes

Newborn baby wrapped in a wool blanket wearing a woolen hat

Parent high fiving child

Burger King sign

Mother talking to teenage daughter about sex

Teenage girl holding her phone

Princess Charlotte

Prince William, Prince George, Princess Charlotte and Prince Louis Father’s Day portrait

Kate Middleton and the late Queen Elizabeth II

Prince Louis, Princess Charlotte, and Prince George

Prince William, Princess Charlotte and Princess Diana