Jaxon Xavier Luthor, who goes by X, is Lex Luthor's illegitimate son.
Lois & Clark
Jaxon was Lex's neglected son, and Lex had told Lois Lane during their relationship that his son had died. Jaxon had a plot to use a virtual reality world as well as his father's mind-washing software to gain power. (Lois & Clark: The New Adventures of Superman: "Virtually Destroyed")