Another idea is that Hermione gets influenced by a dark magic book that she thought was just a regular old magic theory book. The book slowly plants ideas in her head that Harry's power is too dangerous and must be curbed. As a result, she might start to use hexes on Harry in a misguided attempt to keep the peace at Hogwarts.
One possible storyline could be that they are forced into a marriage due to some dark magic spell or a political maneuver in the wizarding world. They then have to navigate their new relationship while dealing with the shock and opposition from their friends and family.
One possible plotline could be that Harry says something unkind to Hermione during a heated argument about a school project. This makes Hermione feel betrayed and sad. But later, Harry realizes his mistake and tries to make it up to her.
Another idea is that there's a misunderstanding. Hermione might think Harry has done something truly unforgivable, like accidentally harming a loved one of hers in a spell gone wrong. Without proper communication, she jumps to conclusions and starts working against him, thinking she's in the right.
The theme of generational trauma could also be present. Maybe James Potter's actions are influenced by something in his own upbringing or past experiences, and that in turn affects Harry. It could show how past mistakes and traumas can be passed down through generations, and how Harry has to face and overcome this cycle. Also, it could explore the theme of forgiveness, whether Harry can forgive his father for the hurt caused or not.
First, they would need to have an honest conversation. Hermione would have to admit what she did wrong and why. Harry, being the forgiving person he is, might be able to start to understand her motives, even if he doesn't agree with them right away. For example, if she was under the influence of a spell, once she's free from it, she can explain that and Harry can see it wasn't really her.
Another storyline could be that Harry is alone as he tries to break a curse that has been placed on him during the Goblet of Fire events. The curse is making him see things that aren't there and is slowly draining his magic. Since he doesn't know who to trust, he tries to find a cure by himself. He travels to different parts of Hogwarts and even outside the school grounds in search of answers, all while feeling the loneliness of being on his own.
One possible storyline could be that she has to hide her pregnancy from her enemies who would use it against her. Another could be that she discovers new magical powers related to her pregnancy.
One possible storyline could be Harry's struggle to prove his innocence while in Azkaban. Maybe he discovers some dark secrets within the prison walls that are related to a larger threat to the wizarding world. Another could be his attempts to escape and the friends he makes or enemies he encounters during the process.
One possible storyline could be that in a battle against a powerful dark wizard, Harry sacrifices himself to save Hermione from a fatal curse. Another could be that he gives up his life to protect Hermione from a dangerous magical artifact that is about to explode. Or perhaps he takes on a deadly disease that was meant for Hermione, knowing it would cost him his life.
One possible storyline could be Harry's struggle to accept his elven heritage. He might initially be confused or even ashamed, but then come to embrace it. Another could be that his elven side gives him unique magical abilities that help him in his battles against Voldemort. For example, he could have enhanced senses or a natural affinity for certain types of magic.