"The Stepfather" is the only known (real) name of the titular antagonist of the film The Stepfather and its sequels Stepfather II: Make Room For Daddy and Stepfather III', where he was played by Terry O'Quinn in the first 2 movies bu in the third film, Stepfather III, he is portrayed by Robert Wightman (a change explained by the fact he gets plastic surgery).
Little is known of the Stepfather's life history, not even his real name. A few subtle clues are given during a few of his rants to himself when he's alone (or thinks he is), suggesting he was the victim of an abusive father. He is a serial killer who is obsessed with extremely conservative family values, and his M.O. is to find an unmarried, divorced or widowed woman, preferably with children, and begin dating her under an assumed name with a made-up personal history. Whenever the family he attempts to create inevitably doesn't live up to his extremely demanding standards, he suffers a mental and emotional breakdown and flees, creating a new identity and life for himself somewhere else, usually murdering his wife and stepchildren before doing so.
Although he has done this numerous times prior to the events of the first film, the Stepfather's first noteworthy alias was Henry Morrison. Under this name, he married a woman with several children. Exactly what happened isn't known, but things went wrong and the Stepfather murdered the entire family and left. As Morrison, he was a bearded man with long hair and glasses. He shaved the beard, got rid of the glasses and cut his hair short (in actuality he is balding and wears a toupee), transforming himself into real estate agent Jerry Blake, who then went on to romance and marry a single woman named Susan, who had a teenage daughter named Stephanie. Although Susan was smitten with "Jerry," Stephanie didn't like him, and the feeling was mutual; the Stepfather dislike his stepdaughter's rebellious streak and the fact that she saw a psychiatrist.
Stephanie began suspecting her stepfather was the notorious Henry Morrison, and confided in her psychiatrist Dr. Bondurant. Bondurant looked into Jerry's past and started becoming suspicious as well, prompting the Stepfather to beat him to death with a wooden plank in a house he was selling. In the meantime, his brother-in-law from the Morrison marriage, Jim Ogilvie, was hunting him to avenge his murdered sister. Realizing his Jerry Blake persona was quickly in danger of falling to pieces, the Stepfather hurriedly began setting up a new life as a man named Bill Hodgekins, and even started dating a single woman named Dorothy Rinehard while still married to Susan. As Hodgekins, he took off his toupee to show off his receding hairline, wore glasses and a false mustache. A slip of the tongue gave things away to Susan too soon, and he attacked her, knocking her unconscious while Stephanie was upstairs.
When Jim Ogilvie showed up, he hesitated when it came time to shoot the man he'd known as Henry Morrison, allowing the Stepfather to stab and kill him. He then pursued Stephanie with the intent to kill her, but Susan got Jim's gun and shot her erstwhile husband, badly injuring him. Stephanie then stabbed him in the chest with a knife. The Stepfather fell down the stairs and was initially thought to be dead, however he survived, and was taken into custody for the multiple murders he'd committed, and committed to an insane asylum in Puget Sound. Since he was arrested while in his Jerry Blake persona, this was the name he was admitted to the asylum under. He was treated by psychiatrist Dr. Joseph Danvers, who the Stepfather found intensely interesting and sought to emulate. After killing Danvers and a security guard, the Stepfather escaped and assumed the identity of psychiatrist Dr. Gene Clifford. He killed a salesman and stole his money and his car, and moved into a new subdivision under the Dr. Clifford identity, where he immediately began attempting to woo real estate agent Carol Grayland, a recent divorcee with a son, Todd.
Complications arose, first from Carol's ex-husband Phil and then from her friend Matty, who didn't think "Gene" was who he said he was. She looked up the high school he claimed to be from and discovered that there had been a Gene Clifford there, but he was a different looking person from the psychiatrist her friend was dating. The interference of both Phil and Matty forced the Stepfather to murder both of them. He stabbed Phil to death with a broken bottle and strangled Matty. Carol eventually figured out the truth and confronted "Gene" about where he'd gotten a certain brand of wine (he had in fact taken it from Matty's house after killing her). Losing his temper, he attacked Carol, who was saved by her son Todd, and the Stepfather was badly injured yet again when the claw end of a hammer was buried in his chest. However, he survived and escaped.
He took the name Keith Grant and hired a back alley doctor to do plastic surgery to change his appearance, after which he murdered the doctor. He continued his efforts to find the perfect family, murdering anyone who got in his way or tried to dig too deeply into his past, before finally meeting his end in a woodchipper.