Joel Tennyson
From Ben10versepedia
Appearing in "My Big Fat Alien Wedding", Joel is Max's nephew and a fellow member of the Plumbers. Having developed a relationship with an alien Sludgepuppy named Camille (despite there being a war between the Plumbers and Sludges for years), Joel marries her in hopes of reaching a truce between the two sides. While the ceremony did not go as well as planned, thanks to the bride's parents, the marriage was made succesfully with the Tennysons' aid.
see also: Tennyson Family