Grin was the nickname of a Gutter drug dealer, since he almost never smiled.
Biography
Grin took over Pyke Lane, turf operated by rival drug dealer Orphy Jones, by murdering Jones. One of Jones' lieutenants, Markus Ralian, became an employee of Grin's.
His chief lieutenant was Jules Antoine Dale, who would become known as Fagin. Grin was seen on the street as just muscle, with the brains being Dale.
Dale murdered the Grin with a T20 pistol and took over Grin's operation, including Ralian.
References
DeCandido, Keith R. A. (November 28, 2006). StarCraft: Ghost: Nova. Simon & Schuster (Pocket Star). ISBN 0-7434-7134-2.