The boy had been declared brain dead following the July 6 accident in which a personal watercraft ran him over as he and a 15-year-old girl were being towed in an inner tube behind a boat.
A friend of the family -- whose name was not reported -- told WSB-TV, Atlanta, Glover died of heart failure Saturday.
DJ Greg Street of radio station V-103 tweeted: "Lil RG is an Angel now, Ryan, Tameka, Usher & the whole Glover Family we gotta make him proud!"
Glover is one of two children of Usher's former wife Tameka Foster and Atlanta television executive Ryan Glover. Usher and Foster were locked in a bitter custody dispute over their two sons -- Usher V and Naviyd -- but Usher relented on his demands following the accident.
Funeral arrangements for Kile were pending, a spokesman at Atlanta's Willie A. Watkins Funeral Home told The Journal-Constitution.