Foxy Brown’s brother is going to jail.

The hot-tempered rapper’s brother, Gavin (Pretty Boy) Marchand, copped to felony identity theft Thursday for using fake credit cards to go on a Madison Avenue birthday shopping spree.

He faces 2 1/2 to 5 years behind bars when he’s sentenced Sept. 28. Marchand, 36, who has dabbled on stage as Foxy’s sidekick, spent $8,000 in luxury goods and went to pay his alcohol tab at a trendy Midtown Manhattan night club, court records say.