Dib is the son of Professor Membrane. Whether or not Membrane is Dib's biological father has not been confirmed. However, it has been said that later in the series, it would have been revealed that Dib and Gaz were created by Membrane in his lab. Nevertheless, the fact that they share similar traits to their father indicates that they were created from their father's own genetic material; thus, they are in a sense his biological children.
MembraneEditThe Professor is a man of science and logic, so he finds Dib's obsession with the paranormal silly, and believes it is only a temporary insanity and Dib will grow out of it. However, Membrane was not surprised when Dib was committed to The Crazy House for Boys in the Halloween episode.
In the Halloween episode he even said "So, I find you here, son. I suppose it was only a matter of time. You know better than to use my tools for your parascince!"
Membrane is very embarrassed by his son's interests, especially when foreign delegates came to visit his house in The Sad, Sad Tale of Chickenfoot. However, these moments of shame are usually very brief, because most of the time Membrane is so busy he forgets he even has a son. It could be argued that Dib's sister, Gaz, is the "favorite child". However, it could also be implied that he cares for both of his children the same, since he refused to go to the "Family Dinner Night" without Dib, even though Gaz was ready to go, in Bloaty's Pizza Hog and he overcompensated the harm made to Dib in each accident after his short death with a mech and weapons in Bad, Bad Rubber Piggy.There are several times in the series that he doesn't recognize Dib when he's standing right in front of him, instead calling him "little boy". Most of the time, Membrane isn't around, and instead has a computer to watch his children. There is only one day a year that Membrane spends time with his son, their annual "Family Dinner Night".
Dib doesn't seem to mind that his dad ignores him, and often counts on the fact that Membrane thinks he's crazy, as said in Gaz, Taster of Pork. There are times when Dib wishes his father would remember him, like in Battle-Dib when he needed a signed permission slip. Dib has a very strong sense of priority, so he finds the annual "Family Dinner Night" with his Dad much less important than saving the world, and even plans on going on a mission the night of the event. In the unfinished episode "The Mopiness of Doom" Dib quit paranormal investigating to work with "real science", to the Professor's delight. Dib was overjoyed to have his father's praise and attention, but eventually gave it up in favor of paranormal research and stopping Zim which greatly upset the professor, but made Gaz happy.