Love across time is also a prevalent theme. Stefan might meet someone in a different time period and fall in love. This creates a complex situation as he has to deal with the differences in their time periods and the fact that their relationship may not be sustainable due to the nature of time travel. There are often emotional and difficult decisions involved in these love stories within the time - travel fanfiction.
Another plotline could be that they accidentally travel to the future and have to deal with the consequences of seeing their future selves. They may discover things about their relationship or the vampire world that they didn't expect. Sometimes, they are on a mission in the future to prevent a disaster from happening in their present time. This involves a lot of action and adventure as they try to figure out how to stop the impending doom while also dealing with the strange future world they find themselves in.
One common theme is the clash of different vampire cultures. Since Stefan has his own vampire lore and the Twilight series has its own, seeing how they interact is often explored.
One common theme is redemption. Many fanfictions explore the idea of Katherine seeking redemption and how Stefan might be a part of that journey. Another is the theme of love and obsession. Their relationship was so complex in the show, and fanfictions often play with this idea, showing how their love or obsession for each other can change over time.
Love and sacrifice are common themes. Often, one of them has to sacrifice something for the other, like Stefan might sacrifice his safety to protect Caroline. It shows the depth of their love.
A theme that frequently shows up is redemption. Klaus, being a complex and often villainous character, may be on a path to redemption in some fanfictions, with Stefan either helping or hindering. Also, power dynamics play a role. Klaus is very powerful, and Stefan has his own set of abilities, so how they interact in terms of power is a common theme. For example, in some stories, Stefan has to find ways to level the playing field when dealing with Klaus.
One common theme is the idea of eternal love. Since they are in a supernatural world, their love is often depicted as something that can transcend time and death. For example, in many fanfictions, even if one of them is in danger or seemingly lost, their love remains unwavering.
One common theme is friendship. Stefan and Bonnie often start as friends in the fanfictions. For example, they might be friends first and then face challenges that make their bond stronger.
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.
Love and commitment are very common themes. Since they are married, the fanfictions often explore how they stay true to each other in the face of various difficulties. For example, in many stories, they have to deal with threats from other supernatural beings but their love remains unshaken.