Maybe the marriage law causes chaos in the wizarding world and Fred and Hermione, being the smart and resourceful ones, decide to use this situation to their advantage. They could start a business together, using their combined skills in magic and charm, all while dealing with their new 'forced' relationship. They gradually fall in love as they face challenges side by side.
Another plot could be centered around the challenges they face in their relationship due to the sudden nature of the marriage law. They might have different lifestyles. Fred is more carefree and loves to have fun, while Hermione is more studious. But as they spend time together, they learn from each other. Fred helps Hermione loosen up a bit, and Hermione encourages Fred to be more responsible, which in turn strengthens their bond.
One idea could be that they initially resist the marriage law but gradually find common ground in their love for knowledge. They start sharing potions recipes and Hermione teaches Severus about Muggle literature. Their relationship evolves from a forced union to a real, loving one as they discover each other's hidden depths.
One possible plot is that Fred and Hermione accidentally meet at a wizarding club. They start to have a connection there, but then realize that the marriage law in the wizarding world has some restrictions that could affect their potential relationship. They then decide to find a way around these restrictions, which could involve seeking help from other magical beings or researching ancient magic laws.
Maybe in the fanfiction, the marriage law is a ploy by a dark wizard to disrupt the order in Hogwarts. Hermione and Minerva have to pretend to be happily married to fool the enemy. During this time, they learn about each other's insecurities and strengths. Hermione might introduce Minerva to some modern Muggle concepts that could be useful in their fight against the dark forces, and their relationship gradually turns into a real and deep connection.
A plot could revolve around a marriage law that was created to strengthen pure - blood and half - blood relations. Hermione, being a Muggle - born, faces a lot of opposition. Harry stands by her side and they fight against the discriminatory aspects of the law. They could go on a journey to find ancient magic that could nullify this unjust law. Along the way, they meet different characters who either help or hinder them, and their relationship grows stronger as they face these difficulties together.
Well, a great plot idea could be that they are paired by the Marriage Law and have to pretend to be a happy couple in public for some political or social reasons in the wizarding world. But in private, they are constantly bickering. As time goes on, they find that they can't help but fall for each other. They might also face challenges from Draco's old Death Eater associates who don't approve of his union with Hermione.
One idea could be that the marriage law forces them to live together and they initially clash due to their different backgrounds. But as they get to know each other's true selves, they start to respect and even fall in love. For example, Hermione might introduce Draco to the value of Muggle - born magic and he could show her some of the more complex pure - blood magic traditions in a new light.
One plot idea could be the Oc and Hermione having to navigate the complex rules of the marriage law. Maybe they initially resist but gradually find common ground and unexpected feelings for each other. For example, they could be paired together by the law and at first be at odds, but as they face challenges in the wizarding world together, they start to rely on and care for one another.
One idea could be the initial shock and resistance from both George and Hermione. George might be still mourning Fred and not ready for such a sudden arrangement. Hermione, on the other hand, could be conflicted as she had feelings for Ron. They could start off as reluctant partners but gradually find common ground through their shared love for magic and their determination to fight against the unjust law together.
One idea could be that they initially resist the marriage law due to their different worlds in Hogwarts. Charlie is all about dragons and Hermione is focused on academics. But as they start to spend time together, they discover they share a love for magical creatures in a different way. Hermione starts to see the beauty in Charlie's wild dragon - taming ways, and Charlie is amazed by Hermione's vast knowledge which could be useful in dragon conservation.