Franklin Bernard "Frank" Dunphy is Phil Dunphy's father. He jokes a lot with his son and is first seen during a video chat in "Undeck the Halls". He has a dog, Scout, who he gets really close to while traveling.
In "Travels with Scout", Frank visits the Dunphys to give them the dog, and he seems upset because later on they find out that he really wanted to keep the dog. Claire ends up missing the dog too when he leaves.