A man convicted of a sea scooter crash that killed Usher's 11-year-old stepson has been sentenced to four years in prison.

The incident in July 2012 on Lake Lanier near Atlanta killed Kile Glover and left another teenager injured.

A jury found Jeffrey Hubbard "guilty of homicide by vessel" last month.

In addition, he was found guilty of several other charges including serious injury by vessel and reckless operation of a vessel.

Investigators said the sea scooter Hubbard was riding hit the children as they were being towed on an inner tube.

Hubbard's defence lawyers said he tried to avoid the children and that what happened was a tragic accident.

Since the incident, a bill has been introduced in America which lowers the blood-alcohol limit for boat drivers to match the car driving limit.

The bill also requires a boat safety education course for those operating motorised vessels bought after January 1998.

Glover was the son of Tameka Foster Raymond and Atlanta television executive Ryan Glover, and had reportedly been raised by Usher since the age of four.

The singer was married to her between 2007 and 2009.

They have two children together, Usher Raymond V and Naviyd Raymond.

Last year, Usher won a court battle for emergency custody of their two sons.

It was after their eldest child, Usher Raymond V, got stuck in a swimming pool drain at the musician's home.