Well, a common theme is the reimagining of the wizarding world with them as a couple. It could involve how they would raise their children in terms of magic education and values. Also, there is often the theme of them facing threats that were not in the original story but are now relevant because of their relationship status. For example, new dark wizards might target them as a powerful couple.
One common theme is the exploration of polyamorous relationships. Since Harry is marrying two people, it delves into how such a relationship can work in the context of the Harry Potter world. Another theme could be the challenges they face from the wizarding society which might not be fully accepting of such a relationship at first.
One common theme is friendship. Since Harry and Hermione are such close friends in the original series, fanfics often explore the depths of their friendship further, like how they support each other through tough times at Hogwarts.
One common theme is friendship evolving into love. Since they are such close friends in the original series, many fanfics explore the idea of that relationship deepening romantically.
One common theme is cultural exchange. Since Viktor is Bulgarian and Hermione is British, fanfics often explore how they share their respective cultures with each other. Another theme is the idea of an alternative relationship. In the original books, Hermione ends up with Ron, so these fanfics offer a different romantic path for her. Also, there's often a theme of acceptance, both from their friends and the wider wizarding community who have to get used to their unexpected union.
One common theme is them facing new threats together as a married couple. They might use their combined skills and knowledge to combat dark forces. Another theme could be their family life, like how they would raise their kids with a mix of their values and magical abilities. Also, there could be themes about their relationship with other characters as a married couple. For example, how Ron would react and how they would maintain their friendships while being in a romantic relationship.
One common theme is friendship - turned - love. Since they start as friends in the original series, fanfics often explore how that deep friendship can transform into a romantic relationship. Another theme is facing challenges together, like battling dark wizards or solving magical mysteries as a couple.
Another theme is power and knowledge. Since Hermione is known for her intelligence, fanfics often focus on how she and Harry use their combined knowledge and power to overcome challenges. For example, in some fanfics, they discover new spells or magical artifacts together. It also often shows how their different strengths complement each other in difficult situations.
Common themes include rewriting the love triangle. Instead of Ron - Hermione - Harry, it becomes Harry - Hermione. There are also themes of self - discovery for both Harry and Hermione. As Harry realizes his love for Hermione, he might also discover new things about himself. And often, there's a theme of overcoming obstacles, like the disapproval of their friends or the chaos of the wizarding world.
One common theme is Hermione's rule - breaking. Since she is usually a stickler for rules, seeing her break them in a 'naughty' way can be interesting. For example, she might break a curfew to explore a mystery in the castle.
One common theme is self - discovery. Hermione might be portrayed as realizing her true feelings for another female character as she grows older at Hogwarts or after the events of the books. Another theme could be the challenges they face in a wizarding world that may not be fully accepting at first. Also, friendship - to - love transitions are often explored.