What is an alien-human hybrid?
A hybrid is the genetically manipulated product of alien and human DNA as part of the colonization project run by the Syndicate.
The biological daughter of Dana Scully conceived as part of the Syndicate Project to create an alien/human hybrid.
Dr. Ernest Calderon
He was an alien/human hybrid who worked at the Prangen pharmaceuticals company and provided special medical service to Emily Sim as part of the Syndicate's hybridization experiments.
They were Human-Alien hybrids cloned after two hybrids originally created by the colonists. These original visitors had come to Earth in the 1940's in order to have a part in colonization. The Gregors' plan and actions were not sanctioned, but they still pursued hybridization experiments using human fetuses obtained in abortion clinics where they worked. These clinics were scattered around the United States. The Gregors participated in the creation of a Samantha Mulder clone series and these female hybrids, who considered the Gregors their fathers, became their partners on this project.
She was the daughter of William and Teena Mulder, as well as the sister of Fox Mulder.
They were a series of hybrid clones produced from female abductees' ova. They were employed by the Syndicate in the colonization project. The individual they were cloned after is unknown, but it is possible he was the son of a Syndicate member. Kurt Crawford was the name of one man in the Crawford series, but since the rest of them are not named, this name is also used as a reference to the whole group, similarly to the Gregor or Samantha Series.
He was a hybrid clone and a member of the resistance against the Syndicate who exhibited healing and shapeshifting abilities. He gained public attention after saving the lives of several people following a shooting in a fast food restaurant. It would seem that this Jeremiah Smith was one of six clones who all worked at the Social Security Administration in different states.
He was a chess prodigy who first met FBI Agents Mulder and Scully in 1998. For reasons unknown, he carried within him alien DNA and was capable of reading others' minds. During this time, he was targeted by the Syndicate because of his ability. After an assassination attempt on Praise failed, the Syndicate sent the Cigarette Smoking Man to kidnap him. While guarding Praise, Diana Fowley was intentionally shot and the Cigarette Smoking Man took Praise away. He was then seen getting into a car with the Well-Manicured Man and Alex Krycek.
She was a repeater, or a multiple abductee, critical to the plans of the Syndicate. She was the ex-wife of the Cigarette Smoking Man and mother of Special Agent Jeffrey Spender, as well as "Patient X," the primary test subject in the project to develop an alien/human hybrid.
He was the son of Detective Miles and a resident of Bellefleur, Oregon. He claimed to have been under temporary alien control several times in his life. After one final abduction, Miles was genetically altered into a human/alien hybrid, and became a super-soldier.
What is a super soldier?
Super-soldiers are human replacements that look human but are actually a type of alien. Fearless and virtually unstoppable, these aliens are not directed by anyone and are answerable to no-one except their own biological imperative to survive. They want to knock out any and all attempts by humans to survive the alien colonization of Earth and were created to aid in the extraterrestrial repopulation of the planet. Their collective name, "super-soldiers," derives from the aliens themselves, but was often used cynically by humans.
All information taken from the X-Files Wiki.