Glover and a 15-year-old friend were floating on inner tubes in Georgia's Lake Lanier when they were struck by a jet ski, according to TMZ. Both children were airlifted to Egelston Hospital in Atlanta following the accident. Glover's friend also suffered serious injuries.
A representative for Egleston Hospital was unreachable at press time.
Glover's mother is Tameka Foster, who was married to Usher Raymond from 2007-09. Raymond and Foster are reportedly present at Egelston Hospital with Glover.
Celebrities have already taken to Twitter to offer their sympathy to Raymond and Foster.
"My deepest prayers go out to Tameka, Usher and both of their families right now," Diggy Simmons wrote Sunday night, while Fantasia posted, "Everyone PLEASE pray for Usher and Tameka's son! This is the time they really need your prayers!"
Usher's seventh studio album, Looking 4 Myself, debuted at No. 1 on the Billboard 200 chart upon its release last month.
The singer and Foster share two sons, 4-year-old Usher Raymond V and 3-year-old Naviyd.