Marco was the lover of Estefania.
Although married to Jimmy Lishman in accordance with her father's demands, Estefania has a romantic affair with another man named Marco. Pleased by this news, Jimmy and Phillip Gallagher manage to smuggle him into the United States, and Jimmy permits them to be together.
Marco turns out to be very abusive toward her, causing her to take up residence at the Gallagher's.
Patching Things Up
Estefania and Marco manage to patch things and continue to live with each other while Jimmy continues his romance with Fiona Gallagher.
Caught by Nando
Jimmy deals with the sudden appearance of Estefania's father, Nando. He abducts him and brings him to the apartment where Estefania's been living at where he lovingly greets his daughter. However, Marco comes out of the bedroom stark naked in front of everyone. Angered by this, Nando quickly shoots Marco in the head killing him instantly and then proceeds to shoot off his genitalia while Estefania screams in rage at her father. He then forces Jimmy to help dismember Marco's body and dispose of it in Lake Michigan.