Marty Jay Williams is the tertiary antagonist in GTA: Vice City Stories and the leader of the Trailer Park Mafia. He is the husband of Louise, main love interest of Victor Vance and the brother-in-law of Phil Cassidy. Marty has connections to poor gangs and is involved in prostitution rackets. He married Louise and had one child together.  Marty is believed to a pedophile in the game. Early in the story, Victor Vance met Marty through Phil Cassidy and was disgusted at Williams' treatment of his wife. Marty hired Victor to help his criminal business and fight the Cholos. He also had Victor help with extorning money.

Loiuse moved out from Marty's place and raised her child with her sister. Marty however kidnapped Louise and intending to make her a prostitute but was stopped by Victor Vance.