Two entries with the name Joshua.
Joshua
According to the pedigree of Grufudd Hiraethog, the son of Evgen, father of Garcelos, and an ancestor of Igraine.
Joshua
Joseus, Josué, Josue
Son of Bron, brother of Alain, and father of Joseph of Arimathea in the Grail histories.
With Alain, he journeyed to the Strange Land, converted King Kalafes of the Terre Forraine, and established Corbenic (Carbonek), the Grail Castle. He inherited the land upon Kalafes’s death, and became the first Grail King. He married Kalafes’s daughter and passed the throne to his son, Aminadap (Aminabad). He succeeded his brother Alain as guardian of the Grail, following the normal line of descent for the Fisher Kings.
His descendants included Pellehan, Pelles, Elaine, and Galahad. John of Glastonbury makes him an ancestor of Arthur himself, through Igerne (Igraine).
Sources
Vulgate Estoire del Saint Graal | 1220-1235
Cronica sive Antiquitates Glastoniensis Ecclesie | John of Glastonbury, mid-14th century