Warhawk

Rex was the son of John Stewart and Shayera Hol.  Named after John's former marine buddy Rex Mason.

At first, Warhawk wasn't impressed when Superman brought Batman into the JLU to seek out who had ambushed Micron. This only worsened when Batman could only barely prevent an assault on Aquagirl. But Warhawk wasn't stupid - he knew that whoever betrayed the JLU, they would come after him at some point. Through remote-control, Warhawk operated his armor into battle and let the traitor destroy the armor.

Warhawk eventually helped Batman uncover the real traitor - a Starro-controlled Superman.

In an alternate timeline in the future created by Chronos, Warhawk, Static, Batman (Terry McGinnis), and Bruce Wayne were the only JLU members that survived. The JLU had to use an abandoned Hamilton Hill High School as their new headquarters, because both the Metro Tower and Batcave were destroyed.

When Justice League members John Stewart, Batman and Wonder Woman traveled to the future to stop Chronos, the JLU saved them from an ambush by the Jokerz. After they escaped, they went back to headquarters where Rex introduced himself as the son of Stewart and Shayera Hol.

These events were erased when John and Batman reversed Chronos' effect in the timestream, but the memory of his son still troubled the Lantern.