Ben 10 season 4 episode 7 : Ken 10

In the future, Ben's son Ken is celebrating his tenth birthday, and to commemorate the occasion Ben gives him an Omnitrix of his very own. However, he equips it with a limiter, unwilling to trust his son to defeat villains on his own. Ken soon befriends a boy named Devlin, and the same night Kevin 11 attacks. Unable to locate the Null Void, which Ben has moved after the events of "Ben 10,000", he retreats. Ken, also unaware of the move, endeavors to find it on his own, only to unwittingly lead Devlin, who is Kevin's son and can transform into his father's mutant form, right to it. Devlin releases his father from the void, but is soon heartbroken to learn that Kevin's only interest is in fighting Ben, not in seeing his son. Kevin is ultimately defeated by the combined forces of Ben 10,000, Ken 10, and Devlin 11, who is later adopted into the Tennyson family.