In "Return to Murder House," American Horror Story: Apocalypse fans got a glimpse at Michael Langdon's home life, years before he came into his own as a bewigged harbinger of the end days. As a teenager, he expressed a desire to be like the ghostly Tate Langdon, whom he referred to as his father. But is Tate Michael's dad on AHS: Apocalypse?
The short answer to that is yes. Technically, he is. But it gets a little more complicated once you start delving into the specifics. Back in Season 1, Tate raped human Vivien Harmon in an attempt to conceive a child for another ghost living in the Murder House named Nora Montgomery. Nora had lost her own child and Tate wanted to give her another one because he cared about her. Being Tate, he went about that mission in the most horrific way possible.
Vivien did get pregnant after that, though it was far from a typical pregnancy. She was expecting twins, with one of them fathered by her husband Ben and the other by Tate. Tate's son was the only baby to survive, and that kid was none other than Michael Langdon. However, during "Return to Murder House," Vivien claimed that neither Ben nor Tate were Michael's real dad. His true father was Satan.
The Murder House has always been a place with bad energy. The spirits trapped inside its walls will perpetuate their own misery upon anyone unlucky enough to wander inside. But Madison and Behold's investigation into the house in Season 8 revealed that there was a reason for it: like the Hotel Cortez, the Murder House is build on a gateway to hell. That contributed to all the horrors that occurred within it and also led to Michael being born.
Vivien believed Michael to be the Antichrist and said his father was "the source of darkness," meaning the Devil. But that was something the show stated back in the first season, too. When psychic Billie Dean Howard delivered her prophecy about the Antichrist, she referred to the child of a human and a ghost as "a perversion of the Immaculate Conception."
The Virgin Mary conceived the son of God after the Holy Ghost whispered in her ear. But, according to Billie Dean, "If the Devil's going to use a human womb for his spawn, he's going to want a little more bang for his buck." If one looks at Michael's creation as an inversion of the Immaculate Conception, then the long-deceased Tate would take the place of the Holy Ghost. He was merely a vessel for Satan's purpose, as the Holy Ghost was for God.
Tate is Michael's father in that his assault of Vivien is what caused Michael to be born; he did not just whisper in her ear. But it's also not that simple (if a ghost impregnating a living woman can ever really be "simple"). The Devil was using Tate to achieve the outcome he wanted, so at the end of the day, Michael is really the child of Satan.