William of Winchester.
William (11 April 1184, Winchester – 13 December 1213), called William of Winchester, William Longsword, or William of Lüneburg, was the fifth and youngest son of Duke Henry the Lion and Matilda of England, Duchess of Saxony, third child and eldest daughter of Henry II of England.
William was born in England during his father's exile; he remained there when Henry returned to Saxony and was raised at Richard Lionheart's court. When Henry died in 1195, William inherited Henry's properties around Lüneburg, near Lauenburg, and in the eastern Harz.
In 1202, William married Helena, daughter of Valdemar I of Denmark. Their only child was Otto (1204–1252), who inherited his father's property and became the first Duke of Brunswick-Lüneburg.