Usher's 11-year-old stepson has been declared brain dead by doctors.

Kyle Glover - the child of the singer's ex-wife Tameka and her former partner Ryan Glover - was unresponsive when he was rescued from Lake Lanier in Atlanta, Georgia, on Saturday after being struck on the head by a passing jet ski while riding on an inner tube and taken to the Children's Healthcare unit at Egleston Hospital in Atlanta, but has "not experienced any brain activity" since being admitted, a source told gossip website TMZ.com.

A decision has yet to be made on whether to take the youngster off life support.

Tameka took to her Facebook page to thank fans and family for their support and urged them to pray for her little boy. "Kyle, You are strong ... You'll be saved I know it. I love you my baby. I need all #Prayers for my son! thanks you everybody! (sic)" the mother of five wrote.

Tameka - who has been undergoing a bitter custody battle with Usher over their sons Usher VI, four, and Naviyd Ely, three - was "extremely thankful" to her former spouse after he reportedly chartered a plane for her to fly back to Atlanta to be by Kyle's side.