Jack Kline (Nephilim)

Lucifer's son is the unborn baby of Lucifer and Kelly Kline.

Background
After Lucifer took possession of President Jefferson Rooney, he had sex with Jefferson's aide and mistress, Kelly, who was unaware of the possession. After their first round, Kelly said she believed Lucifer would make a great father, which inspired Lucifer to sleep with her again and conceive a child.

The conception of the Nephilim was felt by Castiel, who was miles away inside the Men of Letters Bunker. He and the Winchester brothers decided they needed to get rid of the child, as it was the "spawn of Lucifer".

After Sam and Dean successfully re-imprisoned Lucifer, Castiel took Kelly away to a diner. He pleaded with her to get rid of the child, informing her that it was not Jefferson's, but the Devil's. Kelly excused herself to the bathroom and fled the diner. As she rode away in a taxi, she insisted through a phone call that the baby was still hers, and she did not want to get rid of it.

After his mother was rescued by Dagon from Angels trying to kill her and him, Dagon revealed to his mother Kelly that he was a boy. Elsewhere, Lucifer mentioned to Crowley that his son's power is a chip off the old block.

Appearances

 * Season 12
 * LOTUS  (mentioned only)
 * Stuck in the Middle (With You) (mentioned only)
 * Family Feud (mentioned only)
 * Somewhere Between Heaven and Hell  (mentioned only)

Trivia

 * Lucifer's child is the second known Nephilim in the series, the other being Jane.
 * The child is also the first known offspring of an Archangel.
 * It's indicated that the child will be more powerful than any other Nephilim due to being the child of an archangel.
 * Sam had a misconception that the Antichrist was the child of Lucifer because of what he learned from the lore, but Castiel corrected that misunderstanding by revealing that Jesse Turner who was a half demon hybrid was the actual Antichrist in I Believe the Children Are Our Future. It wasn't until 7 seasons later that the actual child of Lucifer would be conceived.