According to Geoffrey of Monmouth, Gorbonian succeeded his father, King Morvid, to the throne in the third century B.C. His reign was a prosperous one, characterized by the restoration of temples.
When he died, his brother Arthgallo succeeded him. Gorbonian’s son, Regin, eventually became king.
Source
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138