In some fanfictions, Logan's sister is an artist in her own right. She could be into painting or writing, and this could intersect with Logan's life in Big Time Rush. Maybe she uses her art to tell the story of Big Time Rush from an outsider's perspective, which could be really interesting. Or perhaps she gets inspired by the music and energy of Big Time Rush to create her best works, and Logan is there to support her as well, creating a symbiotic relationship between their two worlds in the fanfiction.
Another aspect to consider is her relationships with the other members of Big Time Rush. She could develop friendships or even romantic interests with them, which would add a whole new layer of drama and story - building to the fanfiction. Fanfiction writers have the freedom to explore different personalities for her, from shy and reserved to outgoing and bold, depending on the direction they want the story to take.
One popular trope is the sister being a secret musical talent. For example, in some fanfictions, the sister of one of the Big Time Rush members has an amazing voice but is too shy to show it. Another is the sister getting involved in the boys' crazy adventures around Hollywood. She might end up helping them solve a problem related to their music career or a personal issue. A third trope could be a love triangle involving the sister and two of the Big Time Rush members, which adds a lot of drama to the story.
To write a compelling sister character, first give her a distinct personality. For example, if she's really bubbly and extroverted, she'll interact with the Big Time Rush guys in a different way than if she was shy and introverted. Also, give her a goal or a dream. Maybe she wants to be a fashion designer and uses the boys' fame to get some connections in the industry. And don't forget to give her some flaws. If she's too perfectionist, it can cause problems when she tries to help the band with their stage outfits and gets frustrated when things don't go exactly as she planned.
One common theme is family. Since it's about the sister of Big Time Rush members, family bonds are often explored, like how they support each other through the ups and downs of their Hollywood journey. Another theme is friendship. The sister might make new friends in the entertainment world, and those relationships are developed in the fics.
I'm not entirely sure specifically what the 'big time rush little sister story' is without more context. It could potentially be a story related to the Big Time Rush group and a little sister character within their fictional world or in a fan - made story.
Some popular themes could be the little sister's adventures in the world her brothers are part of. Maybe she's trying to find her own place among their fame. For example, she could be struggling with being in the spotlight because of them or trying to start her own music career just like her brothers.
One popular storyline is the boys getting into a huge misunderstanding but their friendship prevails in the end. For example, there could be a situation where they are wrongly accused of something and they have to work together to clear their names, which strengthens their bond.
There might be a fanfiction where a fan wins a contest to style one of the Big Time Rush member's hair. The fan is super nervous but has this amazing vision for a haircut. It could be a story full of anticipation as the fan tries to execute their idea. There could be some obstacles like not having the right tools at first, but in the end, they create a masterpiece haircut that gets a lot of attention from the media and other fans.
Well, in Big Time Rush fanfiction, James often takes on different roles. Sometimes he's the hero saving the day for the band. He might be involved in wild adventures that are not shown in the original show, like a secret mission to find a rare music instrument that could boost their career to new heights.