One reason could be that in the fanfiction, Arthur and Merlin might have a deeper, more complex bond. Maybe they've shared more adventures and secrets that make Arthur value Merlin's presence more. Another possibility is that the writer might be exploring a different dynamic where Merlin offers something unique to Arthur that Gwen doesn't in that particular fictional scenario.
It could be that Gwen unknowingly has some sort of magical influence over Arthur. For example, if there is some ancient magic tied to her lineage that she's not aware of, and it's causing Arthur to focus only on her and forget about Merlin. Another aspect could be that Arthur's love for Gwen is so overpowering that it's subconsciously pushing out other important relationships, like the one with Merlin.
One great fanfiction is 'The Once and Future King's Love'. It beautifully weaves the relationships between Merlin, Gwen, and Arthur. It shows their deep friendship and the budding romances in a really engaging way. The author does a wonderful job of staying true to the characters' personalities from the show.
I'm not entirely sure if there is a specific one. While fanfiction can cover a vast range of scenarios, including some that deviate from the expected character relationships. The idea of Arthur cheating on Merlin with Gwen seems rather untrue to the spirit of their relationships in the common Arthurian tales. But in the world of fanfiction, anything is possible.
In the 'arthur picks merlin over gwen fanfiction', the relationship between Arthur and Merlin is redefined in a more profound way. It's no longer just a king - servant or a friendship relationship. It has elements of a very deep bond that surpasses his relationship with Gwen. This change can also affect how other characters view Arthur and Merlin. They might see them as a powerful duo or be suspicious of their new - found closeness, which is very different from how they were perceived in the original story.
Merlin might become even more protective of Arthur. Since Gwen is carrying Arthur's child, Merlin would see it as his duty to safeguard the future of Camelot. He could be more involved in Arthur's personal affairs, which might initially annoy Arthur but eventually he'd come to appreciate Merlin's concern.
One possible motive could be jealousy. Maybe she sees Merlin as taking too much of Arthur's attention and time, and she wants Arthur all to herself. So she uses some sort of magic or spell to make Arthur forget Merlin.
It could also be due to some past trauma. Perhaps Merlin has been through an experience where Arthur was involved in a way that now makes him flinch. Like, Arthur might have accidentally hurt Merlin during a battle training in the past, and now Merlin flinches whenever Arthur makes a sudden move.
One possible reason could be a misunderstanding. Maybe Merlin did something that Arthur misinterpreted as betrayal or dishonesty. For example, if Merlin was secretly helping an enemy for a greater good that Arthur wasn't aware of at the time.
One great 'Merlin Arthur Gwen fanfiction' is 'The Bonds of Camelot'. It beautifully weaves the relationships between the three characters. It shows how Merlin's magic subtly influences the dynamic between Arthur and Gwen. Another one is 'A Triangular Affair' which delves deep into the complex feelings they all share for each other in a really engaging way.
Popular 'Merlin Arthur Gwen fanfiction' often has strong character development. It dives deep into the personalities of Merlin, Arthur, and Gwen, showing their growth and how they interact with each other. For example, it might show how Arthur becomes more accepting of magic because of Merlin and his relationship with Gwen.