Gwyn chronogically had:
-Firstborn/NK
- Gwynevere
(with a first wife with unknown name, it's likely the woman that holds the baby with a sword)

-Filianore
(with Velka goddess of humans, and later of sin and tears.. She was kept as a secret, in the Ringed City, after Velka likely betrayed Gwyn about pygmys and dark stuff he didn't like because could've ended his glorious plans of eternal light)

-Gwyndolin
-Yorshka
(both of which he had with Priscilla, the daughter of Velka and Seath but it's unknown if it was a forced experiment or willfully Velka banging a tantacled white dragon)

To be honest it's more likely that Priscilla is the mother of Gwyndolin AND Yorshka

<3

my wife

кто уморительно поставил?

Now we can go back in march 2016 when DS3 first released and the community started to find incongruences with the lore. Now, for some reason after eating Gwyndolin, Aldrich has visions of Priscilla and as far as we knew there was no reason for that to happen. Not only that but now there is a new character that reminds us of Priscilla, has Seath's tentacles and calls herself SISTER of Gwyndolin and daughter of Gwyn.

See how it makes perfect sense if we take into consideration that Japanese theory that was basically confirmed with Yorshka?

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Gwyn needed someone to carry one the Chosen Undead line after his link, and Gwyndolin was exactly that. An inferior son kept mostly secret from everyone but at the same time accepted as official so that he would be regarded as a god and the highest authority in Anor Londo after Gwyn himself ; someone who would do anything to be accepted by his father"

The japanese description straight up confirms 3 things:

-priscilla is the daughter of a Pale Dragon

-Priscilla is a bastard daugher

-from the japanese description of Seath soul there is basically a bit where it implies there is some sort of marriage between seath bloodline and gwyn. What the japanese fandom has theorized is that this means Gwyn "married" someone related to Seath.

Now let's connect the dots. Seath somehow had a daughter with someone (presumably with a human since Priscilla's tail weapon deals Occult damage) and for some reasons Gywn decided to clap some half-dragon cheeks. Who's the son of Gwyn that's an hybrid, has an affinity with Moon Magic (remember Moon powers > Moonligh > Seath), can cast illusions (like both Priscilla and Seath ) and has a dragon/serpent motif ? Yep, Gwyndolin.

@Djura what i'm saying is the other way around, gwyndolin is the son of priscilla and gwyn.

I'll cit u/dracopo_reddit:
"I know that this theory may sounds absurd but I'll repost something I wrote not too long ago on YT:

The main problem with Gwyn's family comes from some pretty terrible english translations of basically everything related to Priscilla, the conclusion you can get from the japanese ones would sound like some sort of fan fiction in the english community.

This translation was from Japanese to Italian so I'll just summarize them here. (If you want the full italian translation, it's the pinned comment of this video https://www.youtube.com/watch?v=SGzw9NW4DIM&list=PLKS7SOH9fvAlSH9QPcVPc-SoVdfaO52Tt&index=39 )

@Neril

No, Priscilla is the daughter of Seath the Scaleless Priscilla's mother is left deliberately vague but is believed to be Gwyndolin or Velka. Considering attacking her is considered a sin in game, and due to the prevalance of items of Velka in the Painted World of Ariamis, its possible. However nobody really knows for sure besides maybe Miyazaki.

Gwyndolin was male, raised as a female for somewhat vague reasons. This is more akin to Uncle or Aunt, and Niece.

Hope this was helpful.