Lucas Luthor

Lucas Luthor is the half-brother of Lex Luthor and the illegitimate son of Lionel Luthor with Rachel Dunleavy.

Origins
Lionel forced Rachel Dunleavy to give him up for adoption. Despite his claim to Lex that Lucas had died, Lionel located him when he was twelve, and continued to keep up with and remained in contact with him. However, Lucas was never officially adopted and grew up in poverty in various foster homes.

Season 2
Lionel told Lex that Lucas was dead, but Lucas was then shown to be alive in the scene where Lionel was looking at the picture of Lucas.

In 2003, Lex found eighteen-year-old Lucas in Edge City after a seven month search. He helped Lucas narrowly escape from some gangsters who went after him after Lucas was discovered to be cheating at a card game.

Lex brought Lucas to LuthorCorp to meet Lionel and to covertly organize a takeover of the company. However, Lucas turned on Lex because Lionel offered Lucas ten million dollars to sign his share away. Thinking he had Lucas under his control, Lionel and Lucas plotted together to take Lex's share of the inheritance and have him thrown out of the Luthor Mansion.

However, Lucas realized that at age eighteen, he was entitled to a much more sizable inheritance than his father was offering. In addition, Lucas still had bitter feelings about what he saw as his abandonment by Lionel. Through observation, Lucas also realized that Lionel was no longer totally blind. Lucas took control of everything that Lex owned, including the Talon.

When Lucas was found by one of the gangsters, he was saved by Clark. Lex discovered that Lionel set Lucas up and revealed this information to him. When Lucas kidnapped Lex, Clark discovered Lucas' vicious nature and followed him in an attempt to rescue Lex. In a tense confrontation, Lucas threatened to kill Lionel unless Lionel killed Lex.

With help from Clark's heat vision, Lionel got the upper hand and shot Lucas instead, but the gun was filled with blanks. The brothers revealed the kidnapping to be staged; they had plotted together to reveal that Lionel was no longer blind and worked together to restore Lex's position in LuthorCorp. Lex had Lucas placed safely away under his protection. His current whereabouts are unknown.