One common theme is family loyalty. Since they are both Starks, their loyalty to the family name and to each other as family members is often explored. For example, in many stories, they team up to protect the North and the Stark legacy.
Another theme is redemption. Jon, especially, has a complex backstory. In fanfiction, his journey towards redemption and how Sansa helps him in that process or vice versa is often a central plot point. Also, Sansa's own growth from a naive girl to a strong woman can be intertwined with Jon's story, showing how they both evolve and support each other.
Romance is also a big theme. Writers like to develop their relationship from a platonic family bond into something more romantic. They might create situations where they realize their feelings for each other gradually. In some fanfictions, their shared experiences bring them closer together in a romantic way.
Love and romance can also be a theme, not just in a romantic sense between them but also their love for their family, the North, and their people. And of course, there's the theme of survival. They both have to survive in a very harsh and dangerous world, and fanfictions show how they do that, sometimes relying on each other and sometimes on their own wits.
One common theme is the reunion. Given their separation in the original story, many fanfictions focus on how they come back together. Another theme is the exploration of their relationship in the context of ruling the North. Since they both have a connection to the North, it's often explored how they would do it together.
One common theme is family. Their pregnancy often becomes a catalyst for bringing the family closer or dealing with family secrets. For example, in many stories, their unborn child makes the Starks reunite in a more meaningful way.
Love against all odds is also a big theme. Given their complex family relations and the political situations, their love is often portrayed as something that overcomes all these barriers. Another theme is political intrigue. Their marriage is a significant political move, and fanfictions often explore how they navigate the power struggles around them while maintaining their relationship.
Since 'lemon' content is inappropriate, we can talk about common themes in regular Jon and Sansa fanfiction. One common theme is their reunion. After being apart for a long time in the story, their reunion can be full of emotions. Another theme is their cooperation in ruling the North. They both have a deep connection to the North, and their joint rule is often explored.
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.
A common plot is their reunion. After all the turmoil in the series, they come back together at Winterfell. Another is them facing off against common enemies, like the White Walkers or other power - hungry lords. They use their combined strength and wits to protect their home.
One common theme could be family. Their pregnancy could symbolize the continuation of their family line, especially considering the importance of family in 'Game of Thrones'. Another theme might be love and loyalty. It could show how their relationship deepens through the experience of having a child together.
One common theme might be the exploration of their complex relationship. Given their family ties and the history in the 'Game of Thrones' universe, fanfics might delve into how they overcome those obstacles in a romantic and often passionate way.
One common theme is identity. Jon is often exploring his true identity, whether it's his Stark - Targaryen heritage or his role as a bastard turned leader. Another theme is loyalty. His loyalty to the Night's Watch, his family, and the North is frequently explored. And of course, there's the theme of love. His relationships with Ygritte and other potential love interests are a big part of many fanfictions.