Kynes is the Imperial ecologist on Arrakis and also Chani's father. He initially refuses to take sides in the Harkonnen vs. Atreides scuffle but later aids Paul when it becomes clear that the boy has Fremen interests at heart. Kynes also goes by his Fremen name, Liet.
Let's be honest here. Kynes has one major purpose in the novel, and that's to inform the reader about the ecology of Arrakis and to bring up the ecological themes of the novel.
When we first meet him in Chapter 15, Kynes serves as an explanation station. He tells Leto and Paul about the stillsuits, the worms, the desert, the spice, and about spice harvesting. In telling Leto and Paul these things, Kynes also informs us as readers so that we might fully understand the ecology and environment of Arrakis.
At the dinner party, it's D.D.S.S. (different day; same story). Kynes informs the dinner guests about the Fremen tradition of preserving the water of the dead, and wouldn't you know it? We learn something as well. Kynes also has many lines that blatantly point toward the novel's themes of ecology and nature. For example:
"It's a rule of ecology," Kynes said, "that the young Master [Paul] appears to understand quite well. The struggle between life elements is the struggle for the free energy of a system. Blood's an efficient energy source." (16.145)
And he's right on the money. Blood does become an efficient energy source throughout the novel. Literally, the Fremen harvest the human body and its blood for water. Figuratively, blood is expended during the duels and wars, where the winners win by drawing their opponent's blood energy. And that's just one of many such thematic gems Kynes leaves for the reader to find.
Kynes's alter ego, Liet, represents the prophet archetype. But it wouldn't be Dune if he were just a plain old vanilla prophet. Instead, he is a scientific prophet.
Kynes believes that one day, Arrakis will become a paradise, the universe's Eden. Now, he doesn't receive this belief from a vision, or a dream, or even from scrolling over a Ouija board. Picking up where his father left off, Kynes creates his prophecies through scientific facts and ecological understanding.
Using these, Kynes and the Fremen have developed a system of water preservation and ecological alteration in hopes of one day fulfilling their dream. They've built Ecological Testing Stations, and these stations' measurements are supremely accurate, citing the need for only "three per cent of the energy surface—only three per cent—to tip the entire structure over into our self-sustaining system" (30.65). Sure, it lacks a little of the romance and thrill you'd find in a Nostradamus prophecy, but what Kynes loses in frills, he makes up for in having a prophecy his people can actually measure, touch, and work with.
Pardot Kynes is Kynes's father. He is technically dead by the start of the novel, but in Chapter 30, he goes all Obi-Wan Kenobi and talks to his son from beyond the grave—that or Kynes just hallucinated his father's voice. Either way, Pardot serves a similar role as his son, spouting expository dialogue that clues us into the major ecological themes of the story.