Maybe the story is about their rivalry. Sol is jealous of Draco's popularity among their Slytherin peers. He tries to outdo Draco in everything, from academics to Quidditch. This causes a rift between them. However, when Draco gets seriously injured in a Quidditch match, Sol realizes how much he actually cares about his brother. He then helps Draco recover and they reconcile, vowing to support each other instead of competing all the time.
Draco's relationship with other Slytherins might change. Usually, Draco is a leader among them, but with Sol around, some Slytherins might be divided in their loyalty. Some might side with Draco as they always have, while others could be drawn to Sol's different personality. Sol might be more friendly towards students from other houses, like Gryffindors. This could put him at odds with some of the more traditional Slytherins, including Draco at first. For example, Sol could be friends with a Muggle - born Gryffindor, which would shock Draco and cause some tension between the brothers.
Maybe the twin brother has a special power that Draco doesn't. For example, he could be a seer like Trelawney but more accurate. His visions could show him the future of Hogwarts and the wizarding world during the dark times of Voldemort's return. He then tries to use this power to prevent bad things from happening, but Draco is suspicious of his actions and tries to stop him, thinking he's going against their family and the Dark Lord.
Well, they could have a very complex relationship. On one hand, they might be extremely competitive, always trying to outdo each other in everything from academics to impressing their parents. Since they are in Slytherin, they could also team up and be a formidable duo, using their combined wits to get what they want in the wizarding world. Maybe they have a secret pact to protect each other no matter what.
It could lead to all sorts of interesting plot twists. Maybe there's competition or a stronger bond between them.
The twin could change a lot. He might be the one who stops Draco from making some really bad decisions. For instance, if Draco was about to follow Voldemort's orders blindly, the twin could convince him otherwise. This would then change the whole course of Draco's actions and how he interacts with Harry Potter and his friends.
One possible plot twist could be that the secret twin has been living in the Muggle world all this time. When Draco discovers his twin, he has to navigate the challenges of introducing a Muggle - raised sibling into the wizarding world. This could cause a stir in the Malfoy family, as they have strong pure - blood beliefs.
They might have a really close, protective relationship. His brother could be the one who always has Draco's back. Like when Draco gets into trouble with other students or is under pressure from the Death Eaters, his brother steps in to help him out, even if it means going against the family's traditional views sometimes.
The fanfic could explore how the twin brother's presence affects Ruby's development. He could be more reserved or cautious, which might balance out Ruby's sometimes impulsive nature. For example, in a mission, Ruby might be eager to charge forward, but her brother could hold her back and suggest a more strategic approach. This dynamic could lead to character growth for both of them.
Well, in a fanfiction like this, perhaps Percy's twin brother was separated from him at birth due to some prophecy or dark magic. The twin could have been raised by an enemy of the gods. As he grows up, he starts to question his loyalty to those who raised him when he begins to discover his true heritage. Eventually, he and Percy meet and have to reconcile their differences while also dealing with the threat that the twin's 'adoptive' side poses to the world of the gods.
One possible plot could be that the twin brother has a very different personality from Naruto. Maybe he is more reserved and studious while Naruto is brash and energetic. The twin could secretly be training in a different type of jutsu, perhaps more focused on genjutsu while Naruto is into rasengan and other offensive ninjutsu. Their relationship might start off rocky as they compete for recognition in the village, but eventually they come to realize they are stronger together and support each other in battles against powerful enemies.