Ben 10 Alien Force

Five years after the original series, a 15-year old Ben Tennyson must put the Omnitrix back on to rescue Grandpa Max from a new foe: the Highbreed and their DNAlien servants, who are joined by the Forever Knights. Unable to complete this task by himself, he is joined by his cousin Gwen and a reformed Kevin. Along the way, they meet the children of other Plumbers, many of whom have powers similar to Ben's previous alien forms as a result of an alien parent. With their help, Ben, Gwen, and Kevin must fight to protect the planet.

Aliens:
Swampfire
Big Chill
Alien X
Spidermonkey
Humongosaur
Jetray
Echo Echo
Goop
Chromastone
Brainstorm