I've been reading Frank McLynn's biography of Charles Edward Stuart (Bonnie Prince Charlie) and discovered the story of his daughter, Charlotte, which I hadn't ever come across before.
Charlotte (1753-1789) was the illegitimate daughter of Charles and his mistress Clementina Walkinshaw. However the Jacobite prince battered Clementina and she left him taking her seven-year-old daughter with her. Because of her illegitimate status, Charlotte spent a good part of her life in various convents unable to marry and estranged from her father. He didn't recognize her until 1784 by which time he was an sick old alcoholic. She nursed him tenderly until he died.
A couple of years later she died too. She had never married.
However — and this is the interesting bit — Charlotte had a secret which she managed to keep from everyone including her father. She had had a relationship with the Archbishop of Bordeaux, Ferdinand Maximilien Mériadec de Rohan, and borne him three children - the third having been born just a few days before she rushed to Italy to be by her father's side. The children were brought up in secrecy by her mother mostly in Switzerland. The secret wasn't discovered by historians until, get this, the 1950s.