At first, their relationship would be full of hostility. Harry would be angry about being forced into this marriage with Severus, who he has had a complex history with. Severus, on the other hand, might be indifferent or even disdainful.
One possible plot development could be that at first Harry is extremely resistant. He might try to find ways to break the forced marriage. Maybe he'll seek help from his friends like Hermione and Ron. They could try to look for magical laws or loopholes to dissolve the situation.
Harry might develop from being resistant to the marriage to being more open - minded. He realizes that Severus is not just the strict teacher he once thought. For Severus, he may start to soften his tough exterior. He begins to see Harry not as James Potter's son but as an individual with his own merits.
There are indeed such fanfictions. Some explore really interesting concepts within this odd scenario. For example, in some stories, the forced marriage is a part of a dark plot by Voldemort to gain more power over the wizarding world through Harry. Others might focus on how Harry copes with this situation and tries to find a way out while also dealing with his complex feelings towards Voldemort. It's a very unique concept that can lead to some very creative storytelling.
Yes, there are some fanfictions with this rather strange premise. You can often find them on various fanfiction websites like Archive of Our Own (AO3). Just search for the relevant tags.
One reason could be some sort of ancient magical law or prophecy. Maybe there's a hidden clause that says for the greater good of the wizarding world, they need to be married. It could be related to some power or protection that their union might bring.
In some fanfictions, the forced marriage could lead to a situation where Harry and Severus have to protect each other from external threats. Harry's status as 'The Boy Who Lived' makes him a target, and Severus's past associations also put him in danger. As they face these threats together, they start to rely on each other. This mutual reliance then turns into a deeper emotional connection.
One reason could be for the sake of exploring different relationship dynamics. Fans want to see how Harry would react in a situation that is completely out of his control, like a forced marriage. It adds a new layer of drama to his character.
One common theme is power struggle. Since Snape has his own power and influence in the wizarding world, and Harry is the 'Chosen One', a forced marriage between them could be a way for different factions to gain control. Another theme could be identity crisis. Harry would surely struggle with his identity as a Gryffindor hero being married to Snape, a former Death Eater and Slytherin.
Yes, there are some. You can start by looking on fanfiction platforms like Archive of Our Own. However, the idea of Harry being forced to marry Snape is quite an unusual and often dark or complex concept in fanfiction. Some stories might explore this in the context of a magically - bound contract or some sort of political intrigue within the wizarding world.