A hero from the DC Animated Universe and Earth-12.
During their term on the Justice League, John Stewart and Hawkgirl began a romance that lasted until Hawkgirl's betrayal of the Justice League. After that, Stewart began something with fellow leaguer Vixen. However, during a trip to the future, John Stewart met Warhawk who called him "Dad". This baffled Stewart, but Warhawk did explain what had happen. It turned out he was the child of John and Shayera. When John returned, he decided not to tell Shayera immediately. He did eventually tell her but he also told her he wouldn't be destiny's puppet. So it is unknown if the child is still in the future or not, but Dini did vaguely hint that John and Shayera get back together some time in the future.
In Batman Beyond, Warhawk is a member of the Justice League. When members of the team are being attacked and nearly killed by means of sabotage, he suspects Terry. When a bomb was launched out of Gotham, Warhawk and Terry attempt to stop it. Warhawk soars ahead to stop it and is seemingly killed by the bomb's detonation. It is later revealed that Superman was behind the sabotage and was under the control of a Starro.
Justice League Unlimited
In the future, Warhawk is one of the members of the JLU. Even further in the future, he seems to be one of the last members along with Terry McGinnis and Static. Originally, Rex was hostile towards Terry because Superman allowed him to join without the team's consent which angered Rex. Eventually, however, he and Terry formed an alliance and became friends.
In the episode "Epilogue", Rex appears as one of the final members of the Justice League along with Terry McGinnis, a future Green Lantern and a future version of Aquagirl.
Rex is half-Thanagarian and half-human. Because of this, he does not have organic wings like his mother. Instead, he uses a pair of wings formed from Nth Metal which allows him to fly. He also wears a protective armored suit which has razor-sharp talons. It has been assumed that due to being half-Thangarian, Rex has enhanced strength, stamina, and durability. Although far from invulnerable, he has been shown to have some resistance to injury. A unique quality he showed in later publishings was the ability to mentally manipulate Nth Metal into any shape and form he desires, giving him a limited form of ferrokinesis.
There is some speculation whether Warhawk was inspired by Golden Eagle or may even have crossed paths with him during the years which gave him the idea to become a hero. Bruce Timm and Paul Dini have neither confirmed nor denied these rumors.
Warkhawk was created for the Batman Beyond episode "The Call", where he is shown to be a future version of Hawkman and a member of Justice League Unlimited.
In the Justice League Unlimited episode "The Once and Future Thing, Part II: Time Warped", his origin was retconned. It has been established that he is the son of John Stewart and Shayera Hol, his real name is Rex Stewart.