Harry and Bella are the key characters. Harry is a well - known character from the original series, and in this fanfiction, his role is extended to being a big brother. Bella, as a baby, is a new character in this context. Her character development could be interesting as she grows up under Harry's care. She might inherit some of Harry's traits or develop her own unique ones. And depending on the direction of the fanfiction, other minor characters could be added to enhance the story, but Harry and Bella will always be the main characters driving the plot forward.
One possible plot could be that Harry has to protect Bella from some sort of magical danger in their world. Maybe there are dark wizards after Bella because she has some special power, and Harry uses his skills and knowledge to keep her safe.
Love and friendship are also common themes. The baby sister may find love among the supernatural beings or form strong friendships. For example, she could become friends with some of the werewolves while also having a connection with the Cullens. It adds a new layer to the existing relationships in the Twilight world.
Bella might be very empathetic. Since she's in a family full of complex emotions, she can sense when Damon is feeling particularly broody or when Stefan is stressed. So she tries to comfort them in her own way, like making them a special meal or just sitting and listening to their problems.
Well, a frequently seen theme is the integration of the baby sister into the Twilight - inspired world. This could involve her discovery of the supernatural elements that Bella is already aware of. Also, growth and self - discovery are common. The baby sister often goes through her own journey of finding out who she is, especially in relation to being in Bella's shadow or forging her own path. In addition, friendship is a theme, as she makes friends in Forks and how those relationships compare to Bella's friendships.
One idea could be that Bella is a sweet - natured girl who is caught in the middle of Damon's wild ways and Stefan's more reserved nature. She might look up to Stefan as a role model for being good, but at the same time be intrigued by Damon's sense of adventure. In the fanfiction, she could end up having to choose sides when a big crisis hits their family, like an attack from a powerful vampire enemy.
There is a fanfiction called 'Bella's Little Sister's Adventure'. In this story, the baby sister embarks on her own journey in the Twilight world, facing challenges and making unique friendships. It's a great read if you like seeing a different perspective in the Twilight universe. The author does a good job of integrating the new character into the existing world and storylines.
Their parents' old friends could be main characters. They might come to check on Harry and his sister, bringing gifts and stories about their parents. These friends could offer guidance and protection when needed.
Another interesting one is 'Baby Sister to the Boy Who Lived'. This fanfiction delves deep into how the baby sister's existence changes the dynamics not only within the Potter family but also in the wizarding world as a whole. It explores her growing up in the shadow of her famous brother, yet finding her own identity and making a mark in the magical community.