After being snubbed by the professor Fry decides to seek out his extended family, and finds that the Professor's parents are still alive.
He seeks them out and develops a bond with them, and it makes the professor jealous as well as bringing up painful memories.
It turns the professor's parents didn't allow him to go to university, but rather brought him to a farm. They explain to him that they did it because they were afraid he was going to end up like his older brother and end up in a mental institution.
Farnsworth tells them that he is that older brother, and Bender alludes to the fact that their younger son is dead.
With old wounds healed the professor brings his parents back to the Near Death Star.