Death of Louis XVII
Upon Louis XVI's arrest in August 1792, the royal children were taken to the Temple prison. At first, the daughter Madame Royale and the Dauphin (heir to the throne) Louis-Charles de France were held together with their parents.
Six months later, the King was beheaded, the Queen would follow nine months later, but before that, the children were taken away from her. Eight year old Louis-Charles was "taken care of" by a man whose mission was to brainwash the child and get him to testify Marie-Antoinette abused him...
The Dauphin's health deteriorated while in captivity and he died on the 8th of June 1795. His body was never recovered for having been buried in a common grave, but his heart was kept by the surgeon who had performed the autopsy. In the early 2000's several DNA testings confirmed the heart had Habsbourg-Lorraine genes, putting to rest the theories the Dauphin may have been rescued while in prison.