D'Argo Sun-Crichton was the child of the Sebacean Aeryn Sun and the human John Crichton.
History
His exact parentage is unknown, as he may have been conceived by the duplicate of Crichton who was a crew member aboard Talyn. His gestation in Aeryn's womb was halted by a stasis process that is automatic within Peacekeeper women born into a battle regiment, but the embryo was released from stasis during Aeryn's captivity at the hands of the Scarrans. The Scarrans had intended to derive Crichton's wormhole knowledge from the fetus' DNA, though they were never given the opportunity.
Several weeks later, Aeryn and Crichton were crystalized by Eidelons. Eventually, Rygel XVI was able to retrieve the crystalized pieces and regurgitate them so that the two could be reconstituted. Unfortunately, Rygel failed to regurgitate the fetus, which was now gestating inside the Hynerian. After Rygel was tortured by Scarrans, Aeryn had the fetus transferred back into her own body for the remainder of the pregnancy.
The child was born during the climactic final battle of the Peacekeeper/Scarran War -- the Battle of Qujaga and was named after the Luxan Ka D'Argo, who was killed in the conflict. Crichton quickly bestowed the nickname "Deke" upon the child, as he was uncomfortable using the name D'Argo so soon after his friend's death. It was also an homage to the astronaut from Earth, Deke Slayton, and was partially inspired by the initials "D.C."
Deke was soon the target of a mercenary named Roiin, who tracked the crew of Moya to Hyneria. There, the Crichtons were arrested by forces loyal to Bishan -- who was working with Scorpius. Scorpius believed that Crichton intended to interfere with his plans, and strangled Deke in order to extract his father's secrets. Crichton had no secrets to share, however. Despite the attack, the infant rapidly recovered from the attempt on his life. This -- along with Deke's budding ability to slow time -- led his parents to conclude that there was something highly unusual about him. It was determined that these abilities could not have come from Crichton's DNA, so Aeryn began to investigate her own past.
On Prybella, Aeryn learned that the Crais family had pursued a form of bio-terrorism against the Peacekeepers as retribution for the conscription of Bialar and Tauvo Crais. They contracted a Peacekeeper supplier to introduce dangerous mutatations into the children of Peacekeepers. It was this that had altered Aeryn's DNA.
Deke's abilities continued to manifest and grow. Along with temporal manipulation, the gland located on his spine also proved able to alter reality -- helping to guide Crichton into alternate timelines and unrealized realities.
In his adulthood, Deke became something of a storyteller -- relating his and his father's adventures to eager children in the Uncharted Territories.
Source
D'Argo Sun-Crichton was seen in Farscape: The Peacekeeper Wars and several Farscape comic books.