He had a murder conviction overturned, then accepted a plea deal in the sweeping Fulton County gang and racketeering case involving alleged members of “Young Slime Life.”

Now Young Thug’s brother is back in jail after being arrested Thursday on a gun charge.

Quantavious Grier, who performs under the stage name “Unfoonk,” is charged with possession of a firearm by a convicted felon, participating in criminal street gang activity, not wearing a seatbelt and a window tint violation, Fulton County jail records show.

He was booked into the jail late Thursday, less than six months after taking a plea deal in the massive “Young Slime Life” gang case.

According to arrest warrants, plain-clothes officers were conducting surveillance along Cleveland Avenue in southwest Atlanta when they noticed a black Mercedes G-Wagon backed into a parking spot at a BP gas station. Several people were standing near the driver’s-side door, which raised suspicions of a possible drug deal, an officer wrote in an affidavit.

Police stopped the luxury SUV as it pulled out of the parking lot for an alleged window tint violation, according to the warrants. The car reportedly smelled like marijuana, so Grier was asked to step out.

“I also noticed a handgun in plain view located in the driver side door panel,” the officer wrote. “Mr. Grier advised that the gun was clean, which prompted me to believe he had knowledge of the firearm being there.”

Authorities said they recovered a 9 mm Glock and found “marijuana particles” throughout the vehicle’s floorboard.

As part of his December deal, Grier pleaded guilty to one count of violating the state’s RICO act and one count of theft by receiving stolen property.

He was released from jail after being sentenced to 12 years, with two years commuted to time served and the balance on probation. Under the conditions of that agreement, he was to complete 750 hours of community service and prohibited from possessing guns, court records show.

He was also forbidden from talking to his brother, Young Thug, whose real name is Jeffery Williams, or any of the other 28 co-defendants named in the sprawling Fulton County gang indictment handed down last year.

Prosecutors say Williams is the co-founder and leader of Young Slime Life, which they allege is a southwest Atlanta gang responsible for much of Atlanta’s crime. Young Thug’s attorneys strongly contest the charges, arguing that YSL is simply the name of the award-winning rapper’s record label.

In Grier’s arrest affidavit, an Atlanta detective wrote that he’s been investigating YSL since 2009. He said the group has been engaged in what he described as an “ongoing war” with rival gangs, which resulted in more than 100 shootings and several homicides since January 2015.

The gas station where Grier was arrested, the detective said, is “controlled and used by YSL for the commission of criminal gang activity.”

Atlanta rapper Young Thug speaks with attorney Brian Steel during jury selection in the ongoing Fulton County YSL trial.

Credit: Miguel Martinez

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Credit: Miguel Martinez

Records show this was Grier’s ninth time being arrested in Fulton since 2006.