Havok (AKA Alex Summers) is the younger brother of Cyclops (Scott Summers). In X-Men Legends, Havok is former a member of the Brotherhood. In X-Men Legends II, however, he's no longer a member of the Brotherhood and serves as the pilot of the X-Jet.

In the game, Havok joins the Brotherhood and during their mission to the Russian Nuclear Plant, he uses his powers to protect Magneto from radiation.

Later, Charles Xavier, Emma Frost and Jean Grey travel to the Astral Plane to rescue Illyana Rasputin. At the exact same time, Havok meets Cyclops at the abandoned Weapon X facility in Canada. There, Alex reveals that he's now a member of the Brotherhood and was the one who protected Magneto in Russia, much to Scott's dismay. Afterwards, the two brothers enter a physical battle, because their powers are immune on each other. A short time later, Wolverine arrives and breaks up their fight. At first, Cyclops thinks Wolverine followed him, but the Canadian mutant reveals that he came on his own, due to his ties with Weapon X. Havok then travels with the two through the corridors of the facility, which is now inhabited with GRSO Soldiers and mutant torture chambers. After helping his brother and Wolverine defeat the soldiers and rescuing the mutant prisoners, the last prisoner (a Morlock) reveals that General Kincaid is responsible for all of this, having created "Operation: Vigilance" to not only run tests, but to destroy mutants and wipe them off the face of the Earth. After the mission, Havok refuses to go back to the X-Mansion, due to his affiliation with the Brotherhood and loyalty to Magneto. Despite Scott's plea, Alex says goodbye to his brother and leaves the facility.

Some time later, Havok travels with Magneto and his Acolytes to the X-Mansion in New York. Magneto demands to see Professor Xavier, but the X-Men see him instead, because the professor is currently being held prisoner by Shadow King. After Magneto releases Toad (who the X-Men took prisoner from the HAARP Facility earlier), he talks about Havok's visit at the Weapon X facility and the torture chambers he discovered there. After that, Magneto talks about his new headquarters on Asteroid M and about the war he's prepared against humanity. While Havok claims Magneto is right, the X-Men ultimately disagree. At that exact moment, Sentinels storm the mansion grounds and attack. Havok then aids both Magneto and the X-Men in fighting them. More Sentinels then arrive and capture Magneto, causing Havok and the Acolytes to follow them, while the X-Men remain at the mansion.

Later, after Magneto escapes and crushes the Sentinels, Havok begins to have second thoughts about joining the Brotherhood when Magneto decides to use Asteroid M's Gravitron to cover Earth with asteroids. Believing this act to be madness, Havok tries to stop Magneto, but is easily subdued by Blob and then imprisoned in his room.

Days later, the X-Men finally travel to Asteroid M using equipment they stole from the Sentinel Factory in Europe. After defeating Magneto, Mystique and Sabretooth, the X-Men find Havok imprisoned in his room and release him. After thanking them, he tells them that Cyclops was right about Magneto and decides to join them, which they accept. After this, Havok uses one of Asteroid M's escape pods to travel back to Earth.

After the game is completed, Havok is playable in the Danger Room, along with Magneto and the other members of the Brotherhood.

In the sequel, Havok returns and serves as the pilot of the X-Jet during the team's stay in Canada and Apocalypse's takeover of New York City. He also seems to be seeking redemption for joining the Brotherhood in the previous game.