AELFTHRYTH

'Aelfthryth', also known as Elfrida, (d. 929), was the last child of Alfred the Great, the Saxon King of England and is wife Ealhswith. She had four or five siblings, including Edward the Elder and Ethelfleda.
Aelfthryth married Baldwin II (d. 918), Count of Flanders. One of their descendants, Matilda of Flanders (d. 1083), would go on to marry William the Conqueror, therefore starting the Anglo-Norman line of Kings of England. Through her descendant, Henry I of England, she is also a direct ancestor of the current monarch of the United Kingdom of Great Britain and Northern Ireland, Elizabeth II.