One common theme is the exploration of Snape's hidden paternal love. Another could be the revelation of secrets that were kept from Harry all his life.
One common theme is secrecy. Since it's an 'unknown' relation, the fanfictions often focus on how this secret is kept and what it means for the characters. Another theme is identity. Harry's identity is completely shaken as he discovers he's Snape's son. There's also the theme of redemption for Snape. Maybe he has a chance to be a better father figure to Harry than he was as just a teacher.
Well, family drama is a very common theme. Harry and Snape would need to build a relationship, which would be full of tension and misunderstandings at first. The theme of legacy also plays a role. Harry would inherit not only from the Potters but also from Snape. And there's often the theme of acceptance, both Harry accepting Snape as his father and the wizarding world accepting this new family situation.
One common theme is the struggle between two very different heritages. Harry has the wizarding world heritage from his father and then the Greek god - related heritage from Aphrodite. Another theme could be love and relationships, given Aphrodite's domain. There might also be themes of power, as Harry already has magic and now potentially has powers related to being the son of a god.
One common theme is redemption. Snape has a lot to be redeemed for in the original story, and his relationship with Harry in these fanfictions can be a way for him to find that redemption. Another theme is the breaking of stereotypes. Snape is often seen as the strict and mean teacher, and Harry as the hero. Their marriage challenges these traditional views. Also, the theme of forgiveness is often present. Harry has to forgive Snape for his past actions, and Snape has to forgive Harry for being James Potter's son.
One common theme is the clash of personalities. Snape is often portrayed as brooding and secretive, while McGonagall is more straightforward. Their interactions can be full of tension and underlying respect.
The theme of self - discovery is also quite common. Snape is a character who has always been somewhat of an enigma. In yaoi fanfictions, his relationship with another male character can be a journey of self - discovery. He gets to know himself better, his desires and his capacity for love. And of course, the Hogwarts setting itself is a theme, with its halls and classrooms being the places where these relationships often unfold.
One common theme is redemption. Snape was often portrayed as a complex and somewhat villainous character in the original series. In these fanfictions, being Harry's father gives him a chance to redeem himself in a more direct way. Another theme is family secrets. There are often a lot of secrets about how Snape and Lily got together and how Harry's true parentage was hidden.
One common theme is secrecy. Since it's a big deviation from the original story, the characters often have to keep this new relationship a secret. Another theme is redemption for Snape, as being Harry's father could change how his actions are perceived.
One common theme is redemption. Severus Snape is often portrayed as a complex character in need of redemption, and his relationship with Harry can be seen as part of that journey. For example, in many fanfictions, Harry helps Snape come to terms with his past actions.
A frequent theme is the mending of their relationship. Given their tumultuous history in the original series, Harry might attempt to reach out to Snape in a way that breaks down the barriers between them. This could involve Harry showing kindness and understanding, similar to how one might 'seduce' someone into changing their negative view. Also, there could be themes related to self - discovery for both characters as they interact in this new dynamic.