|Name||Jack Kline Née Rooney|
|Dates||May 18, 2017 (born)|
|Location||North Cove, Washington|
|Episode(s)||12.23 All Along the Watchtower|
Jack Rooney is the Nephilim son of Kelly Kline and Lucifer. He was conceived when Lucifer inhabited the body of President Jefferson Rooney, with whom Kelly was having a relationship. Angels believe that Nephilim are abominations that can destroy worlds; with Jack being the son of Lucifer, it is believed he will also be a force of great evil. However, after the Nephilim, while in utero, gives Castiel a glimpse of the future, Castiel believes Jack will bring peace and paradise to Earth.
Castiel sensed a massive surge of celestial energy and discovers that a Nephilim had come into being. Sam, Dean, and Cass realize that the Nephilim was the spawn of Lucifer. After abducting Kelly, they explained that Kelly was carrying Lucifer's child. At first, she doesn't believe them, but after she places her hand on a bible, it burst into flames. When Castiel takes Kelly to a diner after they exorcise Lucifer from President Jefferson Rooney, Kelly tricks Cass into believing that she is going to the bathroom and escapes. She later calls Cass and tells him that she can't get rid of her baby, stating that she is its mother and its her child before hanging up.
Cass tells Sam and Dean that he had no luck with Lucifer's kid. At first Wally thought it was a joke when he heard them, but eventually realized that it was the truth.
Kelly is eating at a diner, but she doesn't realize that the waitress is an angel. After she was confronted by them, she is saved by Dagon who tells her that she can protect her and her child. She stated that nothing is born evil and that "he could save us all," confirming the baby's gender in the process.
Mick, after learning that Sam and Dean knew about the Nephilim, tells them about how dangerous the child will become if it is born. Dr. Hess later tells Mick that the situation concerning the Nephilim has become more important than their current plan to recruit American Hunters.
Kelly, after experiencing some pain, demands that Dagon takes her to a doctor. He takes an ultrasound of the baby, but he notices something unusual, but Dagon telepathically instructs the doctor to tell her that "everything looks a-okay." After Dean takes Kelly and tries to convince her that she can't have the baby, she tells them that she loves the child and refuses to get rid of it. After Dagon appears to take her away, she willingly goes with her. Later, Dagon chains Kelly to a bed and tells her about how she cannot be trusted. She tries to explain that she was worried about the baby, but Dagon bluntly tells Kelly that the baby will be just fine and that birthing a Nephilim is always fatal for the mother.
After spending a few days refusing to eat, drink, and bathe, Dagon forces her to take her pills and tells her that her son will be born and bring an end to all no matter what happens to her and tells her to take a bath. Kelly tries to kill herself explaining that she can't let what Dagon says happen to the world, despite her love for her child. After she dies, the Nephilim revives her, refusing to let her die. Dagon eventually discovers what happens and tries to pass off her baby saving her as an act to save himself and explains again that she will die when he is born. Ever since then, Kelly is influenced by the powers of the Nephilim and believes that her son is not evil and would bring paradise to the world. After Joshua tracked a disturbance caused when the Nephilim revived Kelly after she tried to kill herself, Castiel, Kelvin, and Hozai were able to track Dagon down. After Hozai was killed and Kelvin was captured, Cass escapes with Kelly and her baby.
After exhausting the information they have on Nephilim, Sam was able to discover that it will be born on May 18. He later discovers that the Grace Extractor can render the Nephilim human to that Kelly and her baby wouldn't have to die.
After communicating with Joshua, Cass tries to bring her to Heaven's Gate, Kelly tries to convince Cass to let her baby be born believing that it could lift the world to its feet rather than bring it to its knees. She explains how she tried to kill herself and how the baby was able to bring her back, but Cass believes that her revival was not proof of goodness and he asks her who will keep the baby on the righteous path when she is gone. Kelly remarked that the baby kicked, but after Cass puts his hand on her belly, he experienced a vision introduced by the Nephilim. Sam and Dean were able to catch up to them and explain that they have a plan to render the baby human with the Grace Extractor, but Kelly refused to let them do it since she wants her baby to be born with all its powers. After waiting in the Impala for Sam and Dean, Kelly takes the keys and drives away form the motel believing that Cass will be able to take care of her baby when she is gone.
After arriving at Heaven's Gate, Joshua appears and tried to tell Kelly not to be afraid, but Dagon appears and kills Joshua. She tells tham that Kelvin told her where they would be going after they escaped. After Sam and Dean catch up, they try to keep her away from Kelly, but she gets the better of them and goes after Kelly. Kelly holds Castiel's hand, but she unknowingly allowed the Nephilim to transfer its power to Cass temporarily and allow him to incinerate Dagon, killing her. Cass, influenced by the Nephilim's power, decides to leave with Kelly Kline to allow her child to be born. When Sam and Dean try to stop them, Cass knocks them out and leaves in his truck, telling Kelly that the Nephilim supposedly showed him the future.
Dean talks to Sam about how the Nephilim was able to mess with Castiel's mind, despite not being born yet.
Cass and Kelly prepare for the Nephilim to be born by purchasing a house in North Cove, Washington, purchasing a truckload of diapers, preparing its room, and Kelly even gave him a name; Jack. She makes a video for Jack when she dies telling him how much she loves him. When she felt a contraction, she unknowingly left a sample of the Nephilim's energy behind which made a rift to an Alternate Universe. After Sam, Dean, Mary, and Crowley arrive to get to Cass and Kelly before Lucifer shows up, they discover the rift made by the baby's energy. Mary tries to help Kelly go into labor while Sam, Dean, Cass, and Crowley try to use the rift to imprison Lucifer.
While they deal with Lucifer, Kelly Kline finally gives birth to Jack in an explosion of light that renders Mary unconscious. When Sam notices the light coming from the home, he goes to check on Kelly, only to find her lying dead in her bed. When he hears a noise, he goes to investigate. He notices footprints scorched into the floor leading to Jack's nursery, where he finds an already adult-looking Jack huddled in the corner, smiling sinisterly as his eyes glow gold.