Love is an overarching theme. It can be brotherly love or a more complex love. Damon's care for Stefan shows that he loves him deeply. And growth is also a theme. Through Damon taking care of Stefan, both of them may grow as characters, learning more about themselves and each other.
I've read a fanfiction titled 'Stefan in Damon's Care'. It's really interesting as it portrays Damon's care for Stefan in different scenarios. It includes Damon making sure Stefan eats well when he's in a weakened state, and also standing up for him against other threats. The author does a great job of showing the depth of Damon's love and care for his brother Stefan.
One common theme is love triangles. Since it involves Damon, Stefan and an OC, often there's a complex love situation. For example, the OC might be attracted to both brothers in different ways.
One common theme is loyalty. Their status as mates often means they have to be loyal to each other no matter what challenges they face, like in many fanfics where other vampires try to break their bond. Another theme is sacrifice. They might sacrifice their own desires or safety for the sake of their mate.
The theme of rivalry also pops up a lot. They are often in competition for things like Elena's love or power in the vampire world. But at the same time, there's the theme of unity. In the face of greater threats, they come together and their bond is strengthened. For example, in some fanfics, when a new, more powerful vampire arrives in Mystic Falls, they put aside their differences to fight it.
Love and sacrifice are also common themes. Stefan and Damon both love Elena deeply and are willing to make sacrifices for her. This could range from giving up their own power to save her life. And there's also the theme of redemption. Damon, who has a darker past, might be on a path of redemption because of Elena's influence. He tries to be a better person, which creates an interesting dynamic in the fanfics.
One common theme is love triangle. Since Bonnie, Damon and Stefan are all connected in the Vampire Diaries universe, the love triangle between them is often explored. It creates a lot of drama and tension.
One common theme is the exploration of a deeper emotional bond. Since they are brothers in the original show, fanfiction often delves into what if there was more to their relationship. Another theme is the struggle with their vampire nature in the context of a new relationship. For example, how their bloodlust might affect their feelings for each other.
One common theme is the struggle for acceptance. Since Bella is the mate of both Damon and Stefan, there's often a plotline about how the vampire community or their friends accept this unusual relationship. For example, they might face judgment from other vampires who don't understand this triad.
In 'fred takes care of hermione fanfiction', a frequent theme is trust. Hermione has to trust Fred enough to let him take care of her. This can be a big step for her as she's used to relying on herself. Another theme can be adventure. Fred and Hermione might go on an adventure together, and during this, Fred takes care of Hermione, making sure she's safe and involved in the fun. There's also the theme of family - like Fred making Hermione feel like part of the Weasley family, which she may lack in some ways as a Muggle - born.
Another theme is the power of love and brotherhood. The fanfictions often show how Sirius' love and care for Regulus can overcome the barriers of the Black family's dark heritage and the dangerous magical world they live in. It's about how that connection between the two brothers can be a source of strength in difficult times.