Well, protection is a big theme. Jacob feels a strong need to protect Nessie. This can lead to stories where he has to fight off threats to her. Family also plays a part. Nessie's family's reaction to her relationship with Jacob can be a theme. Some fanfictions might explore how they come to accept or reject it. And of course, the theme of love against all odds, as they are from different 'races' in the Twilight universe.
One popular theme is the complex relationship between Jacob and Nessie. Since their relationship is somewhat unconventional given their different natures, exploring the challenges they face in being together is a common theme. Another theme could be Nessie's growth and how Jacob influences it. Also, themes related to the supernatural world they inhabit, like how they deal with other supernatural beings in relation to their relationship.
One popular fanfiction might be about their adventures together in the forest. It could explore how Nessie's unique abilities and Jacob's werewolf nature interact in different situations.
One common theme is the struggle between their different natures. Jacob is a werewolf and Nessie is part - vampire, so there can be a lot of tension regarding their instincts. Another theme is loyalty, as they are both loyal to their families and groups.
A major theme is loyalty. Jacob is extremely loyal to Nessie, and this is shown in many fanfictions. They also often explore the theme of family. Jacob becomes like family to Nessie, and how that dynamic affects their relationship is a big part of these stories. Additionally, the theme of power is there as Nessie has unique powers that she has to learn to control, with Jacob sometimes being involved in that process.
One common theme could be forbidden love. Given their different natures, their relationship might be seen as not acceptable in the eyes of some in their fictional world. Another theme might be the exploration of their unique bond, as they are two very different beings coming together.
One common theme could be the challenges they face as a couple during the pregnancy. Another might be how their families and friends react to the news. Also, the anticipation and preparation for the new arrival could be a theme.
A common theme is the exploration of their unique bond. Since they come from different supernatural backgrounds, the fanfiction often shows how they make their relationship work despite the differences. Another theme could be family. They might face issues related to starting a family of their own or dealing with their extended families. For example, how Jacob's werewolf pack accepts Nessie and vice versa.
In the fanfiction, it can expand on the powers that Nessie has and how Jacob interacts with those powers. It might also add new characters that are related to their relationship, like friends or foes that are specifically interested in their union. This adds more layers to the story compared to the original where the focus was more spread out among different characters. Also, it can show more of the cultural aspects of the werewolves and vampires in relation to their relationship, which wasn't fully explored in the original Twilight story.
One common theme is Nessie's struggle to fit in. Being a half - vampire, half - human, she often has to find her place in both worlds. Another theme is her relationships, especially with her family and potential love interests. Family loyalty is also a big part of it, as she is part of the Cullen family.
Power and its implications are another common theme. Renesmee has unique powers that set her apart. Fanfictions may explore how she uses her powers for good or how they attract unwanted attention. Her powers can also be a source of conflict, either within herself as she tries to control them or with others who may fear or envy her abilities. Also, the theme of the coexistence of different species in the Twilight universe, like vampires, humans, and werewolves, often comes up in relation to Renesmee's story.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can search specifically for 'Twilight' Nessie and Jacob fanfictions using the search bar. There are filters you can use to sort by popularity, rating, etc.