One common theme is Sansa's growth. Many fanfics focus on how she matures from a young, sheltered girl into a powerful and independent woman. Another theme is her relationships, like her complex relationship with the other Stark siblings or her interactions with her enemies.
One common theme is family reunion. Given their separation in the original story, many fanfics explore how they come back together and the emotions involved. Another is the rebuilding of Winterfell. They are both Starks and Winterfell is their home, so it's a central aspect in their relationship in fanfics.
One common theme is redemption. Sandor, often seen as a rough and broken character, is on a path of redemption and Sansa can be a catalyst for that. Another theme is the power of unexpected relationships. They come from different worlds in the story, but in fanfic, they often find a connection that defies expectations.
Well, a frequent theme is growth. Both Arya and Sansa have complex characters, and fanfics usually show how they grow and change over time. For example, Arya might become more diplomatic while Sansa could learn some of Arya's survival skills. Also, the theme of redemption can be found in some fanfics. If they had any past mistakes or misunderstandings, they work towards redeeming themselves in the eyes of each other and their people.
One common theme is the idea of new beginnings. Sansa's pregnancy can symbolize a fresh start for her character, both personally and politically. Another theme could be protection, as other characters may rally around her to protect her during her pregnancy.
One common theme is redemption. As I said before, Joffrey is often given a chance at redemption in these fanfics in relation to Sansa. Another theme could be forbidden love, considering their positions and the history between their families. Also, there might be a theme of miscommunication, where their true feelings for each other are hidden due to various reasons in the fan - created storylines.
One common theme is the idea of redemption. Tyrion, often seen as an outcast, and Sansa, who has endured so much, find a form of redemption in their relationship. They heal each other's emotional wounds.
One common theme could be redemption. Writers might try to redeem Joffrey's character so that he becomes worthy of Sansa's love. Another theme could be the power of love to change someone. Since Joffrey was so cruel in the original, fanfic could explore how Sansa's love could transform him. Also, there might be themes related to forbidden love as their relationship was not a positive one in the original context.
The theme of protection is also prevalent. Sandor has a protective streak towards Sansa, which is explored in many fanfics. For example, in some stories, he will go to great lengths to keep her safe from various threats.
One common theme is power dynamics. Given Joffrey's position as a king and Sansa's as a captive in a sense, their relationship in fanfics often explores how power affects their interactions. Another theme is redemption. Some fanfics attempt to redeem Joffrey's character and show how he could have changed for the better in relation to Sansa. And of course, there's the theme of love against all odds, as their relationship was so difficult in the original story.
One common theme is sisterly love. Despite their differences in the show or books, these fanfics often emphasize the deep bond between Arya and Sansa. Another theme is redemption. Arya might be seen as redeeming herself for past actions or feelings towards Sansa.