The Marvel universe is known for its sibling pairs. For instance, Cyclops and his brothers Havok and Vulcan. Another example is Sue Storm and her younger brother Johnny. Individually, these siblings are powerful. Together, they can be nearly unstoppable.

RELATED: X-Men: 5 Reasons Why Cyclops Is The Smartest Summers Brother (& 5 Why It’s Havok)

However, these are not the only related pairs that inhabit Earth-616. Several characters have brothers that readers have forgotten about or simply ignore.

10 Professor Xavier (Juggernaut)

The reason people don't recall Juggernaut being Charles' brother is they're not from the same father. Cain Marko became Xavier's step-sibling when his mother married Kurt Marko. This is also why Cain doesn't have the same mental powers. In fact, Juggernaut isn't a mutant.

Cain gained his strength and durability through a mystic gem he found in an ancient temple. While nearly invulnerable, he's susceptible to mental attacks. Hence, the reason he wears the bulky helmet. Over the years, Cain has gotten over past resentments against his stepbrother and has divided his time between being a hero and villain.

9 Peter Parker (Ben Reilly)

Peter Parker and Ben Reilly in Clone Saga

Technically, Ben Reilly isn't Peter Parker's brother. He's his clone. Still, they have the same DNA, so that makes them siblings. It's somewhat confusing to detail. So, it's best to read "The Clone Saga" stories for the lowdown.

Ben donned the heroic identity of the Crimson Spider for a time, then took over Spider-Man's role when Peter and Mary Jane left New York. He was going to work with his "brother" as another Web-Crawler but was killed by the Green Goblin. Since then, Ben has died and come back to life several times.

8 Union Jack (Baron Blood)

John Falsworth, known as Baron Blood, is one of the oldest villains in the Marvel universe. The reason is simple:  he's a vampire. This was unbeknownst to his brother, Lord James Falsworth, who is the hero known as Union Jack.

RELATED: Dragon Ball: 10 Facts You Didn't Know About Vegeta's Brother

During World War II, James battled his brother while part of the Invaders. As a new age of heroes was born on Earth-616, Baron Blood decided to take on several of them. He was eventually destroyed by Captain America and a new incarnation of Union Jack.

7 Husk (Cannonball)

Within Marvel's superhero teams, the X-Men probably has the largest percentage of siblings. For example, Paige and Sam Guthrie, also known as Husk and Cannonball.

Between the two, Sam was the first to jump into the X-Men fray, joining the New Mutants several decades ago. Once Paige was old enough and could control her mutant powers, she joined the teen group Generation X as Husk. Since then, the siblings have been members of the X-Men, though not at the same time.

6 Wonder Man (Grim Reaper)

In the real world, there are few examples where siblings are so opposite that one is completely evil. Yet, this seems to happen in comic books all the time. Perhaps, if Wonder Man and Grim Reaper had gone to family counseling, they wouldn't be at opposite ends of the spectrum.

Between him and Simon, Eric was known as the black sheep and was even told by his mother that he was born bad. Between that and abusive discipline by his father, it's no wonder Eric became the Grim Reaper. Since his 1968 premiere in The Avengers, he has been a problem for numerous heroes, especially Wonder Man.

5 Hawkeye (Trickshot)

Hawkeye fighting Trickshot

Here's another example of brothers with opposite goals. Yes, Clint Barton indeed started as a villain. However, he eventually realized his ways were wrong. It's the reason Hawkeye has been a long-term member of the Avengers.

RELATED: 10 Best Superhero Sibling Rivalries (& Their Best Fights)

On the other hand, his brother Barney went in the opposite direction. He got away from the circus by joining the army and eventually became an FBI agent. It wasn't until recently that he became a member of the Dark Avengers and the villain Trickshot.

4 Rogue (Nightcrawler)

Rogue and Nightcrawler have always had a close relationship. However, it's not only due to their lengthy memberships in the X-Men. In reality, it's because the two are sort of related.

Nightcrawler's mother is the mutant known as Mystique. She's also Rouge's adoptive mother. If that isn't strange enough, both heroes are also related to Graydon Creed, the son of Mystique and Sabretooth. This would be abnormal in other situations. However, being the X-Men, it's par for the course.

3 Starfox (Thanos)

Starfox MCU Eros Thanos' brother

If you told someone that Starfox and Thanos were brothers, they'd probably scoff. However, no matter how different the two are, they have the same parents.

Starfox is Eros, a human offshoot of Titan's population known as the Eternals. Thanos was born with the Deviant gene. This is the reason the two look and act differently. While Thanos went on to become a deadly nemesis to the galaxy, Starfox remained on the good side of the law and joined groups like the Avengers.

2 Colossus (Mikhail Rasputin)

The older brother of Colossus and Magik, Mikhail has the combined powers of his two younger siblings. He can alter substances and hop between dimensions. He would have been an Omega-level X-Man if he didn't become mentally unstable after a Cosmonaut mission.

RELATED: X-Men: 5 Reasons Why Colossus Is The Strongest Rasputin (& 5 Why It’s Magik)

Today, Mikhail likes to flout his Messiah complex by taking on his siblings whenever possible. He administered the Legacy virus to his sister to get rid of it from his own body. Then, he left Colossus in a rock dimension to die. In other words, he hasn't provided much brotherly guidance.

1 Spider-Girl (Benjy Parker)

Spider-Girl-Mayday-Parker from Marvel Comics' MC2 universe

Benjy Parker is the younger brother of May, also known as Spider-Girl in Marvel's MC2 universe. Though a baby when first introduced, he becomes an integral part of the Spider-Man legacy, although he doesn't understand it.

Though he has organic webbing, Benjy is constantly at risk. At one point, during the "Spider-Verse" saga, May learns her brother is the Scion -- part of a trinity that can help take down the Inheritors. In the end, it's Ben's bravery that encourages May to continue as a costumed hero.

NEXT: 10 Heroic & Villainous Siblings From The DC Universe