It's not appropriate. Fanfiction should focus on exploring characters' personalities, relationships in a non - explicit and more creative, positive way. Such sexual content is not in line with the general values of most fan - created works.
The relationship might become more intense. With the pregnancy, they have to rely on each other more. Jareth may show his softer side as he takes care of Sarah, and Sarah might start to see him in a new light, beyond the intimidating Goblin King.
One way is to explore their friendship. Write about how they learn to understand and trust each other more. For example, Jareth could teach Sarah some magic tricks, and in the process, they build a deeper bond as friends.
A common theme is the exploration of their unspoken connection. Since in the original there's a certain tension between them, fanfictions often expand on that, like in 'The Unspoken Bond' where it's all about their unacknowledged feelings for each other.
One common theme is the power dynamic between them. Since Jareth is a powerful Goblin King and Sarah is a mortal girl, exploring how their relationship develops in terms of power is popular.
Well, aside from Jareth and Sarah, there could also be other characters from the original story that play important roles. For example, the goblins might be characters that are constantly around. They could be either helpful or cause trouble for the newly married couple. Also, Sarah's friends or family from the human world might be in the story. They could be trying to understand her new life with Jareth, or perhaps be worried about her being in the magical world. And who knows, there might be some new magical characters created just for this fanfiction to add more drama and storylines to their married life.
In fanfiction, the idea that they come from two completely different realms, the human world and the Goblin Kingdom, adds to the allure. Their relationship can be seen as a bridge between these two worlds, and how they navigate the cultural and magical differences is fascinating. For example, in some stories, Sarah has to learn the ways of the Goblin Kingdom to be with Jareth, and Jareth has to understand human emotions better. This dynamic makes for a rich and engaging story.
There could be some out there, but a lot of fanfiction platforms have rules against explicit content. You might have better luck looking for more general Jareth and Sarah fanfiction on Archive of Our Own (AO3). It has a large collection, and you can filter by different themes and ratings to find something that suits your taste, but stay away from inappropriate stuff.
They are a popular pairing because of the strong dynamic between them in the original story. Dark Jareth is a mysterious and powerful character, and Sarah is a brave girl. The contrast makes for an interesting relationship in fanfiction.