It could be a love - hate relationship. The twin brother might not like Draco's association with the Death Eaters and try to pull him away from that path. Draco, on the other hand, might see his brother as a traitor to their family's values. However, deep down, they still care for each other. There could be moments when Draco secretly protects his brother from danger, even though he publicly shuns him. And the brother might do the same for Draco when he's in a tough situation.
At first, it could be strained. Draco, being used to being the only son in the family's eyes, might feel threatened by his twin. He could be jealous if his twin shows more magical talent or is more popular at Hogwarts. But as they grow older, they might start to understand each other better. For example, if they face a common enemy, like a bully from another house, they could come together and realize the importance of family.
Their relationship could be complex due to different beliefs. If the twin brother believes in equality between all magical beings and Draco has been indoctrinated with pure - blood supremacy, they would constantly clash. But over time, through shared experiences like surviving a dangerous encounter in the Forbidden Forest or facing a difficult magical task together, they could start to respect each other's views and form a stronger bond.
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.
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, in the fanfiction, they could have a very close relationship. Maybe they protect each other from the dark forces at Hogwarts. They might share secrets that no one else knows, like about their family's hidden past or their own personal fears and dreams.
He could be resentful at first. After all, his parents have kept this big secret from him his whole life. But as he gets to know his twin, he might develop a sense of brotherly love. He may also start to question his family's values and actions in hiding his brother, which could lead to a change in his own character.
It could lead to all sorts of interesting plot twists. Maybe there's competition or a stronger bond between them.
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.
Maybe it was a family secret to protect the twin from some dark force. Or perhaps there was a prophecy involved.
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.
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.
In a fanfiction, their relationship could be complex. Maybe there is some jealousy between them. For instance, Robb might be seen as the more natural leader by their father, which could make the twin brother feel left out. But at the same time, they love each other deeply. When Robb is faced with difficult decisions, his twin brother is the one he turns to for advice, even if they don't always agree.