Jack Kline (Nephilim)

Lucifer's child 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 drove away, she insisted through a phone call that the baby was still hers, and she did not want to get rid of it.

Appearances

 * Season 12
 * Lotus (mentioned only)

Trivia

 * Lucifer's child is the second known Nephilim in the series, the other being Jane.