In many 'in love with a vampire fanfiction', the power dynamic is a theme. Vampires usually have more power physically and sometimes even magically. This can create an interesting dynamic in the relationship, with the human being in a more vulnerable position. Another theme is the exploration of the vampire's past and how it affects their present relationship. For example, a vampire might have a tragic past that makes them hesitant to fall in love again, but the human character helps them overcome that.
The idea of fate also plays a big role. Some fanfictions depict the vampire and werewolf as fated lovers. Despite all the odds against them, they are meant to be together. It gives a sense of inevitability to their relationship. And then there's the theme of discovery. As they get to know each other, they also discover new things about themselves and their own species, which helps them bridge the gap between their two worlds.
One common theme is the forbidden love. Vampires are often seen as dangerous and different, so their love with a human is something society or their own kind may not accept.
One common theme is the struggle against prejudice. Since werewolves and vampires are often depicted as enemies in traditional lore, their love is seen as something that goes against the norm. So they have to fight against the prejudice of their respective communities.
A common theme is the forbidden love. Since the PPG are good - natured heroes and the RRB as vampires might be seen as 'evil' in some sense, their love is against the normal order. Another theme is the power struggle. The PPG have their own powers, and the RRB vampires also have unique vampiric abilities. How they interact with these powers in the context of their love relationship can be a major part of the story.
Love against all odds is a common theme. Since vampires and humans are so different, their love is often seen as something that goes against the natural order.
Well, there's the theme of sacrifice. In many of these fanfictions, either the vampire or the werewolf has to sacrifice something important for the sake of their love. It could be their status in their community, their powers, or even their relationship with their families. Also, the theme of redemption is quite common. For example, a vampire who has been a killer might find redemption through the love of a werewolf. And of course, the power struggle between the two species is always there in the background, adding more drama to the love story.
One common theme is the struggle between immortality and mortality. The vampire is immortal while the human has a limited lifespan, and this creates a lot of emotional turmoil. For example, in many stories, the vampire has to face the fact that their human love will age and die, or the human has to decide if they want to become a vampire to be with their love forever.
One common theme is forbidden love. Vampires are often seen as different and dangerous, so their love with humans is usually against some rules or norms. For example, in 'Twilight', Edward is worried about his vampire nature harming Bella.
Another theme is immortality. Vampires are immortal, and when they fall in love with a mortal human, there is a big contrast. The vampire has to face the fact that the human will age and die, which adds a lot of drama to the love story. Just like in many classic vampire love stories.
Love against all odds is a common theme. Since Brick is a vampire and Blossom might be from a different world or have different values, their love has to face many obstacles.