Both Oscar and his brother grew up alongside Willy Valerio, Armando Torres, Henrique Bardas, and Luis Lopez; all of whom were at some point involved in the drug gang known of as the Northwood Dominican Drug Dealers until the group got taken down resulting in Luis' arrest. Like Luis Lopez, he is said to be involved in illegal street fighting. His criminal record includes possession of a controlled substance with intent to sell in 1998 and Grand Theft Auto in 2005.
In The Ballad of Gay Tony, Armando and Henrique ask Luis if he had seen Willy Valerio or the Gomez Boys recently to which Luis responded no, referring to them as fools. Oscar and Luis do meet up at one point in the game though during a Club Management mission involving a botched drug deal between Oscar and Al Di Napoli. Oscar and Luis seem to have no bad blood between them, asking how each other are briefly and parting ways when the cops arrive as Oscar states as he's fleeing "You're bad luck Lopez!" A reference to their first bust years earlier.
Reported to be concerned about his brother's involvement in the criminal underworld.
In the months leading up to the release of The Ballad of Gay Tony, many fans speculated that Oscar Gomez, along with his brother and Willy Valerio would play a prominent role based on information in the LCPD Database that described them as being close associates of Luis Lopez. Interestingly, this is reflected in in-game dialogue as well when Armando tells Luis that the LCPD constantly question him about Luis' association with the Gomez brothers. Despite the fact that Luis has not seen them in years, the LCPD appear to be under the incorrect impression that Luis still works with them, explaining the flawed information found in the LCPD database.