The Chicago Fire season 12 finale shocked viewers when Jack Damon revealed he was Kelly Severide’s half-brother, but just a few episodes later, Damon left without giving closure to his story. During the season 13 premiere, lots of changes were underway in Firehouse 51. Chief Dom Pascal replaced Boden in Chicago Fire season 13, while Damon and Severide were adjusting to the revelation that they are related. The two brothers were getting along as Damon looked to Severide for guidance as a firefighter and Severide was open to helping his younger brother, but their bliss couldn’t last forever.
https://screenrant.com/chicago-fire-season-13-jack-damon-firehouse-51-return-need/