Gil Thorpe is a real estate agent, and also Phil Dunphy's business rival.
He was first mentioned in "Not in My House". Claire discovers a photo on her computer of a topless woman on a tractor, and she assumes that Luke downloaded it since is the one who used last her computer. But Phil (in interview) says that the picture was his because a man who works with him send it him. Although he first says that doesn't matter who was, he finally says his name: Gil Thorpe.