One common theme is family. Since they are part of the Cullen family, stories often explore their roles within the family structure and how they support each other as family members.
Love and self - discovery are also common themes. Their relationship can be a catalyst for both characters to learn more about themselves and what love truly means, and this is often explored in fanfics.
The theme of sacrifice also appears frequently. Edward might sacrifice his own desires or safety for Carlisle, and vice versa. In some fanfictions, this is shown through them protecting each other from other powerful vampires or from the human world's threats. It's really interesting to see how these themes play out in different fan - created stories.
One common theme is the exploration of family dynamics. Since Carlisle is sort of the father figure in the Cullen family, fanfictions often look at how he accepts or influences Bella's relationship with Edward within the family structure.
Another theme is the struggle with their vampiric nature in the context of their relationship. How their immortality and unique vampire qualities affect how they interact and love each other. For example, some fanfictions explore how they deal with the concept of time and change over the centuries.
One common theme is the exploration of their forbidden love. Since they have a father - son - like relationship in the original series, the fanfiction often delves into how they overcome this social and moral boundary. Another theme is the power dynamic, as Carlisle is older and more experienced in the vampire world compared to Edward.
One common theme is loyalty. Carlisle and Edward have a strong loyalty to each other and to their family. In many fanfictions, this loyalty is tested, for example, when faced with threats from other vampires or when making difficult decisions that could affect the family. Another theme is the struggle with their vampire nature. Carlisle, being more in control, often tries to guide Edward through his own internal battles.
The theme of self - discovery is quite prevalent too. Bella is often portrayed as a character who is on a journey of self - discovery, especially when caught between Carlisle and Edward. This includes understanding her own feelings, her place in the vampire - human world, and her future with either of them.
One common theme is the exploration of forbidden love. Since the relationship between these characters is rather complex in the original Twilight series, fanfiction often plays with the idea of love that goes against the norms set in the original story.
The theme of legacy also pops up often. Carlisle has certain values and a way of life that he hopes Edward will carry on. Fanfictions explore how Edward either embraces or struggles with this legacy. For instance, Carlisle's peaceful co - existence with humans is a legacy that Edward has to decide whether to uphold or not in different storylines.
One common theme is redemption. Edward often feels guilty about Carlisle's death and his time travel is a way to redeem himself. Another theme is the alteration of fate. The idea that by going back in time, Edward can change the future for the better, not just for Carlisle but for the whole vampire clan. And of course, love is also a theme. His love for Carlisle and the rest of his family drives him to take this extreme measure of time travel.
Another theme is friendship. Many fanfics show them gradually becoming friends, like in 'The Friendship Forged', where they start off as enemies but end up having a deep bond.