Kevins Car Alien Force | Ben10

In "Darkstar Rising", he reveals that his father was also a Plumber. He never met his father, but his mother told Kevin stories about what his father did. This is a big gap in the original series because in Ben 10, he said that his parents both left him because of his strange electrical powers but it may have only been an exaggeration on his part, since it is slightly hinted that Kevin's mother remarried, due to him saying, "My father, my real father". 

It's is also possible that he had somehow ended up it foster care, and that it was these parents that left him. At the end of the same episode, Kevin, along with Gwen and Ben become official Plumbers, after which, Kevin leaves to tell his mother about his membership, this suggests that he has now reconciled and rejoined with his family. In Darkstar Rising, when explaining that he wanted to be a Plumber for the sake of being just like his father, it "mostly" served as the reason that he joined the Tennysons in the first place. 

 In the season 3 premeire "Vengence of Vilgax", Kevin is subjected to feedback from the Omnitrix after Ben tampers with it. Because of this, he is unable to revert back to his normal human form.

 Kevin's Car in Alien Swarm

 In Alien Swarm the Live-Action movie, Kevin is seen driving around with his car. The car is a green 2009 Dodge Challenger. In "Single-Handed", he find's Ben's hand extremely funny.