In some cases, it could be the Ministry of Magic itself. If the Ministry is under the control of corrupt officials, they might force the marriage for their own political gain. They could use Harry's popularity and Ginny's family connections to further their own agendas, and thus become the antagonists that Harry and Ginny have to fight against in the fanfiction.
One possible plot development could be Harry initially resenting the forced marriage but then gradually realizing Ginny's true worth. For example, through shared adventures in the wizarding world that they are forced to embark on together, he sees her courage and loyalty in a new light.
One way this plot could develop is through a political or family power play. In the wizarding world, marriages are sometimes used to strengthen alliances. Maybe the Malfoy family and some powerful wizarding families or political forces force the situation. Harry, being female in this fanfic, might initially resist but then gradually find some unexpected common ground with Draco as she gets to know him better in this forced situation.
She would probably be furious at first. Harry is known for her strong will, and being forced into a marriage, especially with Draco, would go against everything she believes in. She might try to fight it directly, using her magic skills to break free from whatever is forcing this marriage.
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 interesting plot twist could be that the marriage is part of a dark wizard's plan to gain control over the wizarding world through Harry. But Harry discovers a hidden prophecy that gives him the power to turn the situation around and expose the dark wizard's true intentions.
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.
No. It's not really acceptable. The Harry Potter series has its own established themes and values, and this kind of fanfiction which involves non - canon and rather inappropriate concepts like forced male pregnancy goes against the general feel of the original story. It's not in line with what most fans expect from fan - created content within the Potter universe.
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.