Gray Daniels was the brother of inmate Carlton "Tug" Daniels.
He was seen in Supreme Allah's crime flashback. Daniels laughs at Supreme when he loses to him at a game of corner dice, and as a result, Supreme shoots him to death and takes back his money left from the game.
He was also seen gambling in a card game along with jiggy walker in his flashback
Gray's brother, Tug, attempts to avenge him in the latter half of Season 4. Tug tries to kill Supreme using a shiv hidden under a table, but he fails and Supreme lives.