Elizabeth Tailboys was a daughter of Henry VIII, but since she was illegitimate, her story isn't told much, though it seems quite fascinating.
Elizabeth Tailboys: Henry VIII’s Forgotten and Fearless Daughter

Elizabeth Tailboys was a daughter of Henry VIII, but since she was illegitimate, her story isn't told much, though it seems quite fascinating.
Augusta Victoria of Schleswig-Holstein was a minor princess distantly related to Queen Victoria, and married a distant relative, the last Kaiser of Germany.
Augusta of Saxe-Weimar-Einsach was just another German princess who became Queen of Prussia. But after the unification of Germany, she became an Empress.
If Poedua hadn't been taken captive by James Cook, we would never have heard of her. We definitely would never have known what the princess looked like.
Catherine Gonsalvus was married off to a "freak" as a joke, but probably had a happy marriage, despite European royalty treating her family like animals.
Iset, also known as Aset or Isis, was just another Egyptian princess. Like many of her sisters, she went on to become the wife of her father, Amenhotep III.
Charlemagne is one of history’s most famous emperors. His mother, Bertrada, also known as Bertrada Broadfoot, was just as fascinating.
Victoria, Princess Royal, the eldest daughter of Queen Victoria, wasn't just a regular Empress. She was a Crown Princess with liberal views she wasn't afraid to share.
Betsy Patterson married Jerome Bonaparte, and when he dumped her on the orders of his brother, Betsy spent the rest of her life travelling Europe like she didn't care.
Marie de Bourbon became Duchess of Montpensier when she was just two years old, and the French royals really, really wanted and needed the girl's money.