Arthur’s brother-in-law in the Didot-Perceval. His daughter, Elaine, is named as Gawain’s niece or cousin.
The Vulgate Merlin mentions a certain Neutres of Garlot (Nentres), who may be identical to Viautre. Neutres’s wife is named Elaine in later texts.
See also
Garloth | The Legend of King Arthur
Source
Didot-Perceval | c. 1220-1230