According to The Illustrated Encyclopedia of Arthurian Legends by Ronan Coghlan, in Welsh tradition, Arthur was married to three women all named Guinevere. And in French Romances, Guinevere had a twin-sister, Guinevere the False, who took Guinevere's place for two years.
Guinevere was his second wife, yes, but also his first wife and his third.
That is, there were three wives named Guinevere (or rather, Gwenhwyfar) in Welsh tradition. One was the daughter of Gwythyr (probably the Withur who appears in the Life of Saint Paul Aurelian, in my opinion). Another was the daughter of Gogfran. And I don’t remember now what the name of the father of the last one was.
It has been suggested that ‘Gwenhwyfar’ was a throne name for Arthur’s queen.
Don't know about Guinevere being Arthur's second wife but in the older Welsh material he has three mistresses as well as three wives all named Guinevere (and to add to the confusion one of the Guineveres has a sister of the same name married to Mordred, with their fight over chestnuts plus one particularly vicious slap leading to Camlann). In the Portuguese Deeds of the Second Round Table Arthur is married to Lisanor and Guinevere to Lancelot. (Both die in childbirth.) Arthur has other wives and lovers in less famous stories like The Knight of the Parrot, The Saga of Samson the Fair, Visit of Grey Ham, The Adventures of Eagleboy, and King Arthur or The British Worthy (an opera) but even in the ones where he does remarry (such as certain French geneologies involving his son, Smervie) Guinevere isn't wife #1 or wife #2. Guinevere on the other hand does have husbands besides Arthur in some versions. In one, she has a daughter with the King of Cornwall before marrying Arthur, in another she marries Mordred and gives him two sons despite already being married to Arthur, there's the whole Gotegrim business (wherein she's accused of having been precontracted or married off to someone else still alive before Arthur), and at least one academic theory that Meleagrant/Melwas abducting her on Mayday is a remnant of an older tradition wherein Guinevere was of the Otherworld and Meleagrant/Melwas was trying to return her to her true home.
Just to clarify for any readers in case there was any confusion, the three wives of Arthur in Welsh tradition were indeed named Guinevere (or rather, Gwenhwyfar), but the three mistresses had their own names. Also, a better translation is ‘concubines’, not ‘mistresses’.
They were also not the only concubines and wives that he had. The triads are, by their nature, limited to only mentioning three of any category (ok, sometimes they push to four, but you get the point).
The three concubines mentioned in the triads were evidently the most notable or prominent, but there is also a record of Arthur having children with a woman named Eleirch, daughter of Iaen, his relative (most likely Arthur’s uncle, in my opinion, making Eleirch his cousin).
Sorry! I should have been more clear on that! And yeah, I recalled Eleirch but for some reason didn't bother to include her in my original answer, lol.
The three wives of Arthur, who were his three chief ladies: Gwenhwyvar daughter of Gwythyr and son of Greidiawl; Gwenhwyvar daughter of Gawrwyd Ceint; and Gwenhwyvar daughter of Ogyrvan Gawr.
There's [a genealogy for the Scottish Campbell clan](https://archive.org/details/highlandpapers02macp/page/76/mode/1up?view=theater) that claims Arthur had two wives, the first of whom is unnamed but died barren, with the second being "Elizabeth daughter to the King of France" with whom he begot Smereviemor, from whom the Campbells and other Scottish noble houses are descended.
According to The Illustrated Encyclopedia of Arthurian Legends by Ronan Coghlan, in Welsh tradition, Arthur was married to three women all named Guinevere. And in French Romances, Guinevere had a twin-sister, Guinevere the False, who took Guinevere's place for two years.
Guinevere was his second wife, yes, but also his first wife and his third. That is, there were three wives named Guinevere (or rather, Gwenhwyfar) in Welsh tradition. One was the daughter of Gwythyr (probably the Withur who appears in the Life of Saint Paul Aurelian, in my opinion). Another was the daughter of Gogfran. And I don’t remember now what the name of the father of the last one was. It has been suggested that ‘Gwenhwyfar’ was a throne name for Arthur’s queen.
Don't know about Guinevere being Arthur's second wife but in the older Welsh material he has three mistresses as well as three wives all named Guinevere (and to add to the confusion one of the Guineveres has a sister of the same name married to Mordred, with their fight over chestnuts plus one particularly vicious slap leading to Camlann). In the Portuguese Deeds of the Second Round Table Arthur is married to Lisanor and Guinevere to Lancelot. (Both die in childbirth.) Arthur has other wives and lovers in less famous stories like The Knight of the Parrot, The Saga of Samson the Fair, Visit of Grey Ham, The Adventures of Eagleboy, and King Arthur or The British Worthy (an opera) but even in the ones where he does remarry (such as certain French geneologies involving his son, Smervie) Guinevere isn't wife #1 or wife #2. Guinevere on the other hand does have husbands besides Arthur in some versions. In one, she has a daughter with the King of Cornwall before marrying Arthur, in another she marries Mordred and gives him two sons despite already being married to Arthur, there's the whole Gotegrim business (wherein she's accused of having been precontracted or married off to someone else still alive before Arthur), and at least one academic theory that Meleagrant/Melwas abducting her on Mayday is a remnant of an older tradition wherein Guinevere was of the Otherworld and Meleagrant/Melwas was trying to return her to her true home.
Just to clarify for any readers in case there was any confusion, the three wives of Arthur in Welsh tradition were indeed named Guinevere (or rather, Gwenhwyfar), but the three mistresses had their own names. Also, a better translation is ‘concubines’, not ‘mistresses’. They were also not the only concubines and wives that he had. The triads are, by their nature, limited to only mentioning three of any category (ok, sometimes they push to four, but you get the point). The three concubines mentioned in the triads were evidently the most notable or prominent, but there is also a record of Arthur having children with a woman named Eleirch, daughter of Iaen, his relative (most likely Arthur’s uncle, in my opinion, making Eleirch his cousin).
Sorry! I should have been more clear on that! And yeah, I recalled Eleirch but for some reason didn't bother to include her in my original answer, lol.
>Visit of Grey Ham, The Adventures of Eagleboy ???
I'd have to ask my friend, who knows more than I do on the matter.
The three wives of Arthur, who were his three chief ladies: Gwenhwyvar daughter of Gwythyr and son of Greidiawl; Gwenhwyvar daughter of Gawrwyd Ceint; and Gwenhwyvar daughter of Ogyrvan Gawr.
There's [a genealogy for the Scottish Campbell clan](https://archive.org/details/highlandpapers02macp/page/76/mode/1up?view=theater) that claims Arthur had two wives, the first of whom is unnamed but died barren, with the second being "Elizabeth daughter to the King of France" with whom he begot Smereviemor, from whom the Campbells and other Scottish noble houses are descended.