At first, their relationship might become strained. Harry, being forced into the marriage, could be cold and distant towards Ginny. However, as time passes, they might start to understand each other's situations better. For example, they could share their fears and frustrations about the forced union, which could gradually bring them closer.
The relationship might also develop in a more magical way. There could be some sort of magical bond that was created when they were forced to marry. This bond makes them more in tune with each other's emotions. As they learn to understand and control this bond, their relationship blossoms. They start to have feelings for each other that are deeper than just friendship, and eventually, they might truly fall in love.
One possible plotline could be Harry initially resisting the marriage due to feeling forced into it, but as he spends more time with Ginny, he discovers new sides of her and gradually falls in love. For example, they might have to work together to face some new dark magic threat in the wizarding world, and through that shared experience, their relationship deepens.
Perhaps the main antagonists are some of the old - fashioned wizarding council members who believe in arranged marriages for political stability. They force Harry into the marriage with Ginny without considering their feelings, and they would oppose any attempts by Harry and Ginny to break free from the forced union.
Another development could be Ginny's perspective. She might be conflicted as well. She loves Harry, but not in this forced way. So she could be torn between her feelings for Harry and her own sense of independence. She may start to rebel against the idea too, which could lead to some interesting interactions between her and Harry as they both deal with the situation.
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.
A powerful and ancient magical being might force Harry to marry. This being could have its own motives that are not immediately clear. It could be related to some prophecy or an old magical law that only this being knows about. Harry would then have to figure out the nature of this being and how to persuade it to release him from the forced marriage.
Maybe in the fanfic, Harry has some unresolved personal issues. He could be haunted by his past traumas, like the death of his parents and his battles with Voldemort, which make him feel that he's not in the right mental state to get married.
Well, in such fanfiction, there could be a plot where Harry tries to find a way out of the forced marriage at first. He might explore magical loopholes or seek help from his friends like Hermione and Ron. However, as time goes on, he realizes that Ginny has always been there for him and starts to accept the situation. Maybe Ginny is also dealing with her own insecurities about the forced marriage, thinking Harry doesn't really want her, but through some shared adventures or conversations, they start to build a real connection.
Their relationship could develop in a rather complex way. Harry, being forced to marry Ginny, might initially try to distance himself. However, Ginny, who has always had feelings for Harry, could slowly break down his walls. She might show him the positive aspects of their union, like how they could be a powerful couple in the wizarding world. As they face external challenges together, like threats from dark wizards who oppose their union, they grow closer and develop a deeper understanding of each other.