15 Anime Heroes Who Have Evil Siblings

When Sanji's mother Sora was pregnant with him and his quadruplet brothers Ichiji, Niji, and Yonji, she was forced to undergo a surgery that would grant her children superhuman abilities and remove their ability to feel most emotions. Hoping to counteract the negative impact on her children, she took medication that made her ill but successfully protected Sanji from the surgery's effects. However, his brothers weren't spared.

As a result, they became cruel people who constantly tormented their brother. Later on, they helped their father try to force Sanji to get married to Charlotte Pudding in the hopes of building a family alliance. 

When Naruto begins, Sasuke is a straightforward hero and Itachi is a straightforward villain. But things soon get more complicated. Obsessed with avenging the clan that Itachi destroyed, Sasuke teams up with the villainous Orochimaru in order to gain the power he needs to take his brother down. After Sasuke finally fights Itachi, he learns that while Itachi did slay their clan, he was forced to do it by one of the cruelest figures in the entire series - Root leader Danzo Shimura. 

Disgusted that a member of his city's government ordered the destruction of his clan, he decides that, actually, he wants to destroy Konoha - the same place Itachi hoped to save. Once a hero, Sasuke becomes a villain - and the formerly villainous Itachi looks a lot more heroic post-mortem.

After fighting alongside his former teammates to stop a literal alien invasion and then having a showdown with Naruto, Sasuke gives up his destructive desires and becomes one of Konoha's most important shinobi. Having a final goodbye with a temporarily reincarnated Itachi helped, too. 

Though the two brothers constantly traded their heroic and villainous positions, in the end, they're both heroes. 

It turns out that Dabi from the League of Villains is actually hero-in-training Shoto Todoroki's long-lost older brother Toya. Both of them suffered from being pushed to the limit by their father Endeavor, but their different experiences with him led to different outcomes.

Shoto was born with a quirk called Half-Cold Half-Hot, which lets him produce and control both ice and fire, while offering resistance to both. This is what Endeavor had been trying to create through having kids, and he was overjoyed. Though his father didn't always treat him well, Shoto was able to find reasons to pursue heroism outside of his father's desires with the help of his friends. 

Meanwhile, Toya's Cremation was powerful but nearly unusable because he lacked resistance to fire and kept burning himself. Though Endeavor told him to stop training, he made it clear that he had no use for Toya outside of his quirk achievements. This led Toya to overtrain until he seemingly passed away. When he recovered from his substantial injuries, he ended up with the League of Villains, hoping he'd be able to use the organization to get revenge on his father and destroy corrupt heroes like him. 

Killua Zoldyck hails from a family of assassins. While he has no qualms about taking lives when necessary, he generally uses his abilities for good. His oldest brother Illumi is a different story. Illumi is devoted to enforcing their parents' wishes, which means monitoring Killua's actions and popping up to rein him in whenever it looks like he's about to stray too far from what their parents want.

While he sometimes takes on a neutral role in Killua's life, he also sometimes openly opposes him. For example, towards the end of the series when Killua liberates their sister Alluka from her in-home prison, Illumi tries to destroy Alluka on the grounds that her wishing power poses a huge danger to the family - but the instant he realizes that Alluka's powers are being used safely, he drops the issue. He's less immoral than he is amoral, but he's probably the biggest obstacle that Killua has to face. 

Natsu Dragneel is a straightforwardly good person whose main goals involve completing missions for his guild and protecting his friends from danger. But thanks to his brother Zeref, his life is a lot more complicated than that. 

Zeref began dabbling in dark magic after Natsu and their parents were destroyed. He succeeded in creating a version of his lost brother who was strong enough to one day end him - which is exactly what he hoped for. Why did he hope for that? Because he was cursed by the God Ankhseram.

This curse made him functionally immortal, and it also made it so he had no choice but to destroy everything he cared about. The only way to avoid causing harm is to stop caring about anyone. In his attempts to undo his curse, he ends up causing a ton of damage and hurting a ton of people, placing him firmly in the category of tragic villain. 

Currently, Hanako and Tsukasa are both ghosts haunting Kamome Academy. While Hanako tries to solve problems caused by spirits, Tsukasa is often the one causing the problems. Not only that, but he also seems to be going out of his way to thoroughly creep Hanako out. 

In life, they were twin siblings - their real names being Amane Yugi and Tsukasa Yugi. Under circumstances that were never fully explained, Amane ended Tsukasa's life. What is clear is that Tsukasa was violent towards Amane and others. Likely, this was an act of self-defense on Amane's part.

In their afterlife, Tsukasa uses the fact that Amane (now Hanako) did this in order to manipulate his emotions. It's a complicated, dark relationship that's even more disturbing in the manga than in the anime.