Luis is of Dominican descent, born in Liberty City, his mother is Adriana Yanira Lopez, his brother Ernesto Lopez and his sister Leta Lopez-Wilkinson. His father was a U.S. Marine who abandoned them while they were young. He was raised by his mother, who also had a notable role in the upbringing of Luis' childhood (and current) best friends, Armando Torres and Henrique Bardas. He also grew up with Oscar Gomez and Alonso Gomez, Teddy Benavidez and Willy Valerio, older kids by three years, ushered most of the neighborhood kids into drug dealing. During a drug war, Henrique mentions that Luis used to rap while Henrique "layed down" the beat. Henrique claims that Luis was a poor rapper because people used to laugh at him when he would rap. He was also scrawnier in those years, as Armando and Henrique recall.
When Luis was 17, in 1999 or 2000, he went to juvenile hall for two years because he shot and injured a teacher who felt up his sister. Armando and Henrique remember spending the summer of 1999 with Luis, meaning it happened during their next school year. Curiously, this does not appear on his criminal record. Not long after his release in 2001, he had been arrested again for Grand Theft Auto. This likely coincides with him taking the blame for a crime committed by Armando and Henrique (neither of whom were caught) and going to prison. During this stint, also two years, he went from being very skinny to being quite muscular. He got his physique by body-building to help against fighting off inmates to keep himself from getting raped or killed. His brother and sister, however, both left Liberty City and started stable lives, with a spouse, children and homes in different small-town suburbs, with little to no interaction with their mother. As a result, she relies on Luis to give her money.
Luis got in police trouble a third time in 2003, for Assault, but avoided prison. This likely coincides with Luis being arrested alongside Oscar Gomez and Willy Valerio - the LCPD goes on for years thinking Luis is still closely connected to them, while in fact this was one of their last times together.
In 2005, when Luis was 22, his life changed when he accepted a job from "Gay" Tony Prince to be a bodyguard. It wouldn't take long for Tony and Luis to see each other as a sort of father-and-son pair. He cut all remaining ties with his old gang (except Armando and Henrique as friends), and paid his supposed last visit to an illegal cage fighting ring (though he would return). By working for Gay Tony, his life became much more positive, and while he lost respect with old friends who saw him as a yuppie, he was introduced to much more money and glamour. Tony once paid Luis to take helicopter-flying lessons for business purposes (as shown from his Higgins Helitours piloting certificate in his apartment, as well as the Club Management mission with Bruce Spade). Unfortunately, Tony was in debt to several loan sharks across the city such as Mori Kibbutz and Ancelotti member Rocco Pelosi, setting in motions TBOGT's events.
Luis begins doing several jobs for Tony, witnessing the bank robbery, meeting Rocco Pelosi & Vince in the introduction. He began doing work for his mother and friends (Momma's Boy, Corner Kids and Clocking Off) then began helping Rocco with his work on missions for Tony; he meet multiple gang officials in peace attempts, all of which wage war nearly killing him and Tony. He would then get The Celebinator (Blog This) off Tony's back. Tony would introduce him to Yusuf Amir, who got Lopez stealing a Buzzard & APC; he would later work for Mori Kibbutz, one of Tony's loaners; after completing This Ain't Checkers and beating Mori in a Triathlon, he got Tony out of his grasp.
Things only turned worse for Tony after a Bahama Mamas meeting in the mission Boulevard Baby also went wrong; Luis, Evan Moss and Gay Tony would later fail to buy $2,000,000 worth of Diamonds, fortunately able to reclaim them that much later. Luis also discovered how Tony had befriended Gracie Ancelotti.
Luis began working for Ray Bulgarin, who had him deal with his Marki Ashvilli situation alongside Timur, his right-hand; after discovering how Luis bought Diamonds that were claimed to be his, he ambushed and betrayed Lopez by having him witness The Cook's dead head and sending snipers, gunman and choppers after him. Having have left him, Luis gets Tony's attention on this; his life is falling apart now.
Thanks to Niko Bellic & Gerald McReary, Gracie Ancelotti is discovered kidnapped; Luis, knowing how she pumped Tony with cocaine, refuses to help; but he is made by Tony to track her down. When the Ancelotti's, following this mission, fail to reclaim her forcefully, Tony and Luis are forced to give away the Diamonds to Niko Bellic in the mission Ladies Half Price.
Luis is later ordered to kill Tony in the mission Party's Over, but kills Uncle Vince, and spares Rocco due to being a made man, and at the cost of a heavy ambush. He later kills Timur and Ray Bulgarin in Departure Time.