Sean "Sweet" Johnson is Carl Johnson's older brother, living in single floor home just next to the Johnson House. As leader of the Grove Street Families, Sweet remained in control of the gang while Carl was away, albeit in a sorry state. Throughout the storyline, Sweet remains caring and dedicated to his family, gang, and neighborhood. Sweet's car license number is GROVE4L, which means "Grove For Life". He drives a Greenwood, which seems to get wrecked constantly, at one point getting driven through a billboard before exploding into a tanker. He and CJ drive an identical car afterwards, causing CJ to say that he "can't believe [Sweet] bought the same bucket-ass car." Sweet responds with "if it ain't broke, don't fix it."

After the death of Brian, Sweet blames CJ, prompting Carl to leave Los Santos. After his return to Los Santos, CJ aids Sweet and the rest of the gang in restoring the GSF to its former glory. This is jeprodized earlier in the storyline however, when Sweet was badly wounded in a shootout with the Ballas and arrested. A large amount of GSF members were killed and Carl was forced out of Los Santos for the remainder of the game until the final missions.

After recovering in a prison hospital, he is placed in prison between two psychopaths. In the left cell a child killer, who wants to rip his throat out. In the cell to the right of him, a white supremacist, who wants to eat his heart. His cellmate is a man called "Horse-cock Harry."

Sweet was released from jail later in the game, after Mike Toreno had agreed to Carl that he would arrange for Sweet's release in return of Carl's many missions done on his behalf. Sweet shows anger and disbelief when Carl tells him about all of the places and things he's done since he was forced to abandon Los Santos, stating that Carl had forgotten about the hood again, and returns to Grove Street. He then helps Carl reclaim various places for the Grove across Los Santos and goes with CJ to confront Big Smoke in the mission End of the Line.

After Officer Frank Tenpenny escapes Smoke's Crackhouse in a firetruck, he hops on the fireladder to keep Tenpenny from escaping. He and CJ then chase Tenpenny across Los Santos until Tenpenny finally crashes in the heart of Grove Street, where he dies from his injuries. CJ is about to shoot him when Sweet stops him, telling him it's over. Sweet would then return home and rebuild the GSF's dominance in the neighbourhood again, for good. In the end missions he is offered drugs by an unamed women but CJ intervenes and kicks her out of the Johnson House .

It is suspected, that Sweet is based on Ice Cube's character, "Doughboy" from Boyz N The Hood, (a movie from which most of the game is based) or the rapper WC. Faizon Love voiced Sweet