One common theme is identity crisis. Merlin has to come to terms with being the son of a man who has persecuted his kind (magic users). Another theme is family secrets. The fact that this truth has been hidden for so long creates a lot of drama.
Power dynamics is a major theme. As Merlin is Uther's son, it affects his standing in Camelot, both in terms of political power and magical power. Also, redemption is a theme sometimes. Uther was not always kind to magic - users, and this relationship can lead to a path of redemption for him in some fanfictions.
One common theme is power dynamics. Given Uther's position as king and Merlin's as his servant, there's often exploration of how power affects their relationship. Another theme is secrecy, as Merlin has to hide his magic from Uther.
It would be very complex. Initially, Uther would be in shock. He has been hunting magic - users, and now his son is one. But he might also feel a sense of protectiveness. Merlin, on the other hand, would be confused and angry at being lied to about his identity. Eventually, they might start to understand each other more. Uther could see the good in Merlin's magic and Merlin could see the reasons behind Uther's actions, even if he doesn't agree with them all.
One common theme is redemption. Uther has been so against magic, but in these fanfics, he often has to face his prejudices when it comes to Merlin. For example, he might realize that not all magic is evil through Merlin's actions.
A popular one is 'Merlin: The Adopted Son'. This fanfiction focuses on how Merlin, as Uther's adopted son, has to navigate the politics of Camelot while hiding his magic. It also explores the relationship between Merlin and Arthur from a new perspective, as brothers in a way, which makes for a very engaging read.
One great Merlin Uther slash fanfiction is 'The King and His Warlock'. It delves deep into the complex relationship between them, exploring their unspoken feelings and the power dynamics at play. The story is filled with emotional moments and beautifully written dialogue.
I'm not sure of a specific title, but in general, fanfictions with this premise often explore the idea of Merlin having to hide his identity as Uther's son. They usually rewrite parts of the original story to incorporate this new relationship. For example, Merlin might struggle with feelings of betrayal towards Uther, who has been so harsh on magic users, not knowing that his own son is one. This can lead to a whole new set of character dynamics and plot twists within the Camelot - centric story.
One possible plot could be Merlin growing up in hiding, not knowing his true identity. Then, as he gets closer to Camelot, strange things start to happen. Magic stirs in him more powerfully, and he begins to have visions related to Uther. Eventually, through a series of adventures and near - misses, the truth is revealed. Maybe Merlin saves Uther's life in a crucial moment, and Uther starts to suspect there's more to Merlin than meets the eye.
These fanfictions are popular because they allow for a lot of character exploration. Uther is a complex character, and when he adopts Merlin, we can see different sides of him. For example, we might see a more nurturing Uther, which is a contrast to his usual strict self. Also, Merlin's character can develop in new ways, like how he might use his magic more openly or subtly within the context of being Uther's adopted son. It gives the writers a chance to play with the existing characters and create new and exciting storylines.
A common theme is the conflict between loyalty and personal beliefs. Merlin has always been loyal to Arthur, but his loyalty to magic and his own kind might come into conflict. This internal struggle is often explored in these fanfictions.