The twin sister of King Meriadoc of Wales.
Orwen’s father, King Caradoc, was murdered by her uncle, Griffin, who then targeted the children for assassination. They were saved by Ivor and Morwen, their foster parents, and taken to hiding in the forest of Fleventan.
In time, Meriadoc was taken to Arthur’s court and Orwen was kidnapped by King Urien of Scotland, whom she later married.
Source
Historia Meriadoci Regis Cambrie | Late 13th century