Placidas le Gays, Placides li Gais
A knight in the service of King Ban of Benoic and King Bors of Gaul. He helped defend his masters’ lands against King Claudas while they were assisting Arthur in Britain.
Later, he was involved in a quest to learn the fate of Merlin for a year and a day.
It is not impossible that Placides li Gais was the nephew of Leonces, but there is no passage to be found connecting the two.
Sources
Vulgate Merlin | 1220-1235
Arthour and Merlin | Late 13th century
Le Morte Darthur | Sir Thomas Malory, 1469-1470