Two entries with the name Cador.
Cador
A baron under Arthur.
He is sent with three others to convey the Roman prisoners to safety. He is probably identical with Cador of Cornwall.
Cador
Son of the King of Cornwall and brother of Guignier, the maiden who married Arthur’s Sir Caradoc.
He was wounded when a knight named Alardin abducted his sister, and became friends with Caradoc when he rescued her. He accompanied Caradoc to Arthur’s court and married Ydain, one of the ladies there.
Source
First Continuation of Chrétien’s Perceval | Attributed to Wauchier of Denain, c. 1200