The version of Ezra Seldom who appeared in the show was from an alternate universe created by The Barkeep to help cure his writer's block. It's likely that another version of Ezra once existed in the prime universe, however, that version is now dead.
Ezra Seldom arrived on Mars some years ago with his wife and baby daughter. His family was slaughtered by lizard men, however, he survived a shot to his gut. Ezra crawled to the nearest town, where he survived. He then spent many years riding the red plains of Mars killing lizard men, until he found and killed the ones that slaughtered his family.
He later was on a wagon train, when he saved another being from choking to death. This being was a member of The Galaxium, and to thank Ezra, he put a measure of The Force Galactic in a trust for Ezra, who only used it after the Galaxium being died. Ezra used his powers to begin looking through the many universes the Barkeep created for versions of his wife and daughter who were alive.
Ezra eventually became aware of the Prime universe. He sent an idealized version of Chesh Glutterfane he found in an alternate universe to fight the real Chesh Glutterfane, but when the idealized version was killed by his prime version, Ezra left to fight and kill Chesh himself. Moments before leaving, the Prime versions of The Red Plains Rider and Pemily Stallwark appeared, banished to that dimension moments earlier by Chesh, much to Ezra's surprise. He summoned Pemily and Red back to the prime dimension, and confirmed Red's suspicion that Ezra was her father, or, a version of him anyway.
Ezra planned to smush all of the universes that the Barkeep had created together, taking the best parts of each one so that only one reality remained, and that reality was filled with only good things happening to everyone. The Red Plains Rider objected, saying that though her parents were dead, she'd been raised well by the martians who took her in, and, though the mistakes she made with Sparks Nevada and Croach the Tracker, she's the person she is today.
Ezra wished for Red to come with him, searching the universes for a living version of Red's mother, so they could be a family again. Croach objected, and said that Red already had a family, the one they had created as a family of friends on G'loot Praktaw.
Sparks realized that though Ezra had already smushed then erased several other alternate universe beings that had been present, he hadn't smushed an alternate, male version of The Red Plains Rider that was present. Sparks suggested that that version of Red, who was the only member of his family that had survived an attack by robot outlaws and hadn't been tempered by being raised by martians nor friendships, had a lot in common with Ezra. He suggested that Ezra and this male version of Red ride together to find a living version of Red's mother, and both agreed.
Ezra restored all the alternate universes to how the Barkeep had created them, and then left with his son to continue their search.