Celestia and Luna might also show up in some fanfictions. Celestia could offer wisdom to Twilight Sparkle's little brother, or Luna might appear in his dreams to give him hints about a mystery he's trying to solve. Their presence would add an element of grandeur and magic to the story, connecting the little brother's small - scale adventures to the larger world of Equestria.
One interesting storyline could be Twilight Sparkle's little brother getting involved in her magic studies. He might accidentally cause some chaos in her study area with his own budding magical abilities. For example, he could make all the spell books float around in a disorganized mess while trying to help Twilight organize them.
First, you can start with his appearance. He could look similar to Twilight but have some distinct features, like a different color in his mane or tail. In terms of personality, he might be more outgoing than Twilight. For example, he could be the type to easily make friends with everypony he meets. This would contrast with Twilight who can be a bit more reserved in new social situations.
In some fanfictions, she could die sacrificing herself for her friends. Twilight is extremely loyal to her friends in Ponyville. So, if there was a situation where her friends' lives were in danger, like from a powerful villain, she might choose to give up her own life to protect them. This would be a very heroic and in - character way for her to die.
Flash Sentry could be a likely groom. He has shown an interest in Twilight in the past and they have had some interactions that could lead to a romantic relationship. Another option could be a completely new character, perhaps a powerful wizard or a prince from a far - off land who Twilight meets during one of her adventures and falls in love with.
A likely candidate could be Discord. He is known for causing chaos and mischief. He might pretend to befriend Twilight Sparkle only to betray her at a crucial moment. Another possibility is Trixie. Trixie has been jealous of Twilight in the past and could betray her out of envy.
One idea could be that the twin brother has a different magical specialty. For example, while Twilight Sparkle is great at magic related to friendship and harmony, her brother could be more attuned to magic of the elements in a different way, like having the power to manipulate natural elements more directly. Maybe he could use his magic to help protect Ponyville from a new, different kind of threat that Twilight's magic isn't as effective against.
There probably are. Fanfiction allows for a lot of creative freedom. Some authors might want to explore the impact of Twilight Sparkle's death on other characters in Equestria. It could be a way to create a really emotional and thought - provoking story, but it's also a bit of a shock considering Twilight is such a central character.
It could be a pony who is extremely extroverted if Twilight is introverted. Someone who loves chaos and spontaneity instead of Twilight's love for order and planning.
Friendship is a very common theme. Since Twilight is all about friendship in the show, fanfictions often explore new aspects of her friendships with other ponies. Another common theme is magic. Twilight being a powerful magic user, her magic and its development or use in different situations are often explored. Growth is also common, like her growing as a leader or a more powerful mage.