Love and sacrifice are common themes. Given her selfless sacrifice for Harry in the original story, fanfictions often explore this further.
One major theme is the power of a mother's love. In many 'Harry Potter and his mom fanfiction', Lily's love is depicted as a force that can even change the course of magic. There are also themes of family secrets. Maybe there are things about Lily's family or her own past that Harry discovers through these fanfictions, which add more depth to their relationship. Additionally, the theme of redemption can also be found, where Harry and his mother's connection helps in redeeming certain characters or situations.
One common theme is the struggle between motherhood and her past as a hero. For example, she might have to deal with her own PTSD from the battles she fought while still being a strong and loving mom.
Love and protection. Since his mother sacrificed herself for Harry, fanfictions often explore how that love still lingers and protects him in different ways.
Adventure is another theme. The girls often join Harry on his quests and adventures. They work together to solve mysteries, fight dark forces, and in the process, their relationships grow and develop in the context of these exciting adventures.
One common theme is the exploration of forbidden love. Since Harry and Lucius are on opposite sides in the original story, their relationship in fanfiction often challenges the norms of the wizarding world. Another theme could be redemption. Lucius might be seen as redeeming himself through his relationship with Harry.
One common theme could be family dynamics. Since it involves Harry and his brother, exploring their relationship, whether it's full of love, rivalry, or a mix of both, is often seen. Another theme might be growth, like how they both develop as characters throughout the story.
Often, there could be themes of self - discovery. Harry might learn more about himself through his interactions with his dad in these fanfictions. Also, themes of acceptance, both of each other and of the situation they are in, can be quite common. The 'lemon' aspect might add an element of sensuality, which could be related to themes of love and attraction within the family context in a fictional and often very different take from the norm.
Some common themes could include internal conflict. The characters would have to grapple with their own feelings and the knowledge that their relationship is not socially acceptable. There might also be themes related to protection. For example, Harry might feel an even stronger need to protect his sister because of their romantic relationship. And the theme of sacrifice could also come up, as they might have to sacrifice their relationship for the greater good of their family or the wizarding world.
One common theme could be time - travel or alternate universes. Since the concept is so out - of - the - ordinary, it often requires a different timeline or reality to make sense. Another theme might be the exploration of family dynamics, as Harry being Tom's mom completely flips the traditional family relationships in the Harry Potter universe.
One popular theme could be exploring the relationship between Harry and his mother in an alternate universe where she survived. For example, how she would guide him in his wizarding education and protect him from Voldemort in a different way. Another theme might be the backstory of his mother, like her days at Hogwarts and the friendships she made that could have an impact on Harry's life.