One common theme is redemption. Many fanfictions explore the idea of whether Tom Riddle could be redeemed through his interactions with Harry Potter. Another theme is the power of friendship or the lack thereof. Since they are on opposite sides in the original story, fanfictions often play with the concept of how their relationship could change if friendship was possible. Also, the exploration of their shared heritage as wizards is a theme. They both have a connection to Slytherin, and this is often explored in fanfiction.
The theme of identity is quite common. Both Harry and Tom have complex identities, and fanfictions often dig deeper into how they perceive themselves and each other. Another theme is the manipulation of magic. Since they are both powerful wizards, fanfictions might explore different ways they can use magic, especially in relation to each other. And the theme of legacy is present too. They both inherit a certain legacy in the wizarding world, and fanfictions can show how they deal with it, like Tom Riddle's connection to Salazar Slytherin and Harry's to Gryffindor.
Well, a frequent theme is the battle between good and evil. In these fanfictions, Harry represents good and Tom Riddle represents evil, and their interactions are centered around this. Time - travel is also a common theme. Fanfictions might have Harry going back in time to change Tom Riddle's path. And the theme of destiny is often there. Whether they are fated to be enemies or if there's a way to change that destiny is a popular concept in such fanfictions. For example, some stories might suggest that Harry is the key to changing Tom Riddle's dark fate.
One common theme is the exploration of good and evil. Since Tom Riddle becomes Voldemort, fanfictions often examine how Harry, as the symbol of good, could influence or be influenced by Tom. Another theme is the power of magic. Writers like to play with different magical concepts and how they might be used by Harry and Tom.
One common theme could be the exploration of an unexpected relationship between Harry and Tom. Since it's mpreg involved, it might also deal with themes of new life and how it changes their dynamic. Another theme could be the blurring of the lines between good and evil as they are brought together in this very different situation.
One common theme is the power struggle. Harry, representing the light side, and Tom, the dark side, often engage in a battle of wills and magic power. Another theme is the exploration of their shared past, like how they are both connected to Hogwarts and the wizarding world's history in different ways.
Another theme is the exploration of power dynamics. Harry has his own power, and Tom is extremely powerful in a different way. Their relationship in the fanfictions often explores how these different powers interact and whether they can find a balance in their romantic relationship. For example, in some stories, their combined powers are seen as a way to overcome greater threats in the wizarding world.
The theme of fate is also very common. The fact that they are soulmates implies a certain kind of fate. Fanfictions often explore how they are meant to be together in some way, even though it seems so unlikely given Tom's actions. For example, some stories show how their connection was predestined by magic itself.
The theme of duality is quite common. They are two sides of the same coin in a way. Harry represents light and Tom represents dark, yet they are soulmates. Fanfictions often play with this duality, showing how they can balance each other out. There's also the theme of self - discovery. Through their connection, both Harry and Tom discover new aspects of themselves that they never knew before.
Love and redemption can also be a theme. Sometimes the OC's love for someone or something makes them try to redeem Tom Riddle from his dark path. This could be a romantic love for Riddle himself, or a love for the wizarding world that makes them want to change him. It adds a layer of complexity to the relationship between the OC and Riddle.
Well, a big theme is the power struggle. Harry is seen as the 'good' and Tom as the 'evil', but being brothers adds a new dimension. Also, the theme of identity. How does being brothers change who they are? It's complex and often explored in these fanfictions. They also might explore the theme of how their upbringing could have been different if they knew they were brothers from the start.
In these fanfictions, a frequent theme is the alteration of the existing plot. A female Tom Riddle can bring a whole new perspective to the events in the Harry Potter series. For example, her relationships with other characters like Dumbledore or Snape could be very different. Also, the theme of love and its impact on her character is often explored. Could she be swayed by love in a way the male Tom Riddle wasn't? And then there's the theme of the nature versus nurture. Is her dark nature inborn or is it a result of her upbringing in the wizarding world?
One common theme is the power struggle. Since Tom Riddle is such a powerful and dark character, the idea of being his mate often involves a struggle between the mate's own values and the power that comes with being associated with him.