Lucas was the high school sweetheart of Carmen Luna who got her pregnant, though he never learned this.
Lucas attended high school with Carmen Luna in Puerto Rico, and the two of them became "sweethearts". However, their relationship ended in Carmen getting pregnant with his child, though she never told him and proceeded to give the baby away to her cousin Josefina. ("Blood, Sweat and Smears")
Years later, Carmen and Lucas' daughter Daniela finds the former and learns the truth of her parentage, though she is dismissed when she asks the identity of her father. She then returns home to find this out, to Carmen's annoyance. Later, when Carmen breaks up with a man named Doug, he phones Danni with the information she needs about her father as an act of revenge against Carmen, who thinks it would be very bad if Lucas were to find out. ("A Time to Spill", "Blood, Sweat and Smears")
Eventually, Daniela meets her birth father and introduces herself. When Lucas wonders if Carmen would agree to meet him again, Daniela decides to return to Beverly Hills to confront her biological mother. However, as she remains furious at Carmen for how they left things, Daniela goes as far as to lie and tell her that she discovered Lucas died before he got the chance to know he even had a daughter. When a heartbroken Carmen re-approaches her, she tells Daniela about Lucas, even giving her a ring that once belonged to him. When Carmen is gone, Danni calls her father and tells him not to fly out to Beverly Hills because, she lies, Carmen doesn't want to see him. ("I Saw the Shine")
- The idea of Lucas showing up as Daniela's father was originally thought up as a three episode arc for the latter half of the fourth season. However, due to the season being limited to ten episodes, the story was pushed back and ultimately left set up to be done the following season, only for the series to wind up cancelled instead.