According to Geoffrey of Monmouth, a king of Britain in the third or second century BC.
Gerontius was the son of King Elidur. Gerontius succeeded his cousin, King Runno. Gerontius’s son, King Catell, succeeded him.
Gerontius is a popular name in British history.
See also
Geraint | The Legend of King Arthur
Source
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138