Grandpa Max Tennyson

 

Maxwell "Max" Tennyson
is the sixty-year old (sixty-five in Ben 10: Alien Force, sixty-six in Ben 10: Ultimate Alien), rather overweight and a bit slow at times, paternal grandfather of the cousins Ben and Gwen Tennyson. Despite his age, Max has shown on multiple occasions to be highly athletic and a formidable fighter. He takes his grandson gaining superpowers and super-abilities in stride and supports Ben in any way he can. Max was once in the Army, had been in the astronaut program, and was a "plumber" and has been through his share of scrapes. Ben and Gwen were ignorant of this at first, believing him to have been a literal plumber. They began questioning this after several incidents in which he displayed knowledge and skills that a plumber would not normally have; everything from military-style hand signals^[4] to a working knowledge of nuclear reactors.^[9] Throughout the first season, it seems that Max knows far more about aliens than he lets on, which climaxes in the season finale, where it is revealed that he and Vilgax are old enemies, with Vilgax even going so far as to call Max "a thorn in his side".
In reality, Max was indeed a plumber, but not the kind that Ben and Gwen thought he was. He was part of an interstellar policing counter-terrorist/black-ops organization called "The Plumbers", which dealt with extraterrestrial, paranormal, and other situations that many others could not handle.^[10] Their base was beneath Mount Rushmore.^[11] The group was disbanded shortly after Max defeated Vilgax for the first time, suggesting that Vilgax had been largely responsible for the various incidents they dealt with.^[10] Max was to have been among the candidates eligible for the Apollo 11 mission, and would have gone were it not for other concerns.^[12]
Max is an old friend of an alien named Xylene. Xylene, like all the other three-eyed aliens of her planet, has the powers and abilities of flight, telepathy, and telekinesis. She had intended to send the Omnitrix to Max, but Ben found it by accident.^[13] Max and Xylene seem to have been romantically involved and work well as a team. Xylene tries to convince Max to form a partnership and travel across the galaxy with her, but Max eventually turns her down twice: the first time due to his duties as a Plumber, and the second time due to his need to look after the kids.
He also had a romantic relationship with an Anodite alien named Verdona. They ended up having two sons, Carl Tennyson, Ben's father, and Frank Tennyson, Gwen and Ken's father. However it seems that their relationship had apparently ended as Verdona left Earth to return to her home planet, Anodyne. She was assumed dead by her husband in "Ben 10: Race Against Time".
In Ben 10: Alien Force, Max plays a part in exposing the Highbreed conspiracy, and once the conflict is over, trains a new group of young Plumbers, at the same time informing Ben and the team of any alien threats.
In Ben 10: Ultimate Alien, at age sixty-six,Max continues to watch for alien attacks. During an encounter with Aggregor in "Map of Infinity", his nervous system is badly damaged. Azmuth has him placed in a Galvan medical tank in order to replace the damaged parts, an operation that is stated to take some time. However, he returns in the two-part season one finale "Absolute Power", his nervous system having been fully restored, and assists his two grandchildren in battling the villainous, Ultimate Kevin.

Kevin Levin

Kevin Ethan Levin
Kevin, is a seventeen year old (eleven in Ben 10, sixteen in Ben 10: Alien Force, seventeen in Ben 10: Ultimate Alien-present) Osmosian (a play on osmosis, meaning gradual absorption) /Human half-breed with the power and ability to asborb whatever matter he touches to form a layer of this matter on his body to protect himself and give him super-strength. His Osmosian blood was inherited from his father, who was a Plumber and one of Max's partners. Unfortunately, Kevin's father was killed in a mission by a vicious alien criminal called Ragnarok which started a downward spiral for him. Kevin became a series villain during the first show from absorbing energy, the very action taboo as it warps an Osmosian's mind as a result. He befriends Ben in their first encounter in order to use the Omnitrix's power to take out his anger on everyone who treated him like a monster because of his abilities. However, absorbing too much of the Omnitrix energy causes Kevin to turn into a chimeric hybrid of the alien forms and swears revenge on Ben for it. Eventually, Kevin ends up at the Null Void where he manages to regain his human form and fully master his abilities under the guidance of an inmate. He eventually manages to escape and became involved with the intergalactic black market. However, his involvement during the Highbreed invasion causes him to team up with Ben and Gwen, leading him to live his dream of being a Plumber like his father, reconcile with Ben, and start a relationship with Gwen over time. Though able to start on a new leaf, Kevin still acted out of his own interests at time and has trouble forgiving others. During Vilgax's challenge to Ben, Kevin accidentally mutated into a being made up of various materials of rock and metal as a result of absorbing Omnitrix energy, gaining the power and ability to turn his limbs into makeshift weapons and stretch them. When the Omnitrix is destroyed, Kevin reverts back to normal, retaining his ability to shapeshift after copying matter, as well as gaining the ability to secrete a liquid form of whatever material he has absorbed or manipulate the material when he is touching it. During the events of Ultimate Alien, Kevin is forced to absorb the Ultimatrix's energy in order to stop Aggregor, sacrificing his noble righteousness and mental stability in the process, now more insane as a result and a monstrous combination of Ben's newer aliens. After absorbing the energies in Aggregor, Kevin goes on a revenge spree against anyone who wronged him. However, unlike when he was eleven, Kevin is more of an anti-villain rather than a true villain, and has shown that he still retains some of his heart and humanity despite going insane after absorbing the Ultimatrix's energy. This is best seen in "The Enemy of my Enemy", when he spared Gwen's life instead of killing her, saying: "The only reason you're alive is because of what you used to mean to me." In the two-part episode "Absolute Power", Kevin had absorbed the powers of Alan Albright, Manny, Helen, Pierce, and Doctor Viktor. Gwen tries to reason with him which occasionally failed. Even the reasoning from Grandpa Max and Kevin's stepfather didn't go through. In a last stand in Los Soledad, Ben as Ultimate Echo Echo managed to bring him down and have the powers drained from him, thus reversing his mutation and restoring his sanity