Stephens was born in Putney, London and was educated at Malory Comprehensive School (currently Haberdashers' Knights Academy), Bromley. He was four years old when picked for the part, which required him to have his blond hair dyed dark brown. In an interview with AMC, director Richard Donner said Stephens got the part after attacking the filmmaker (at Donner's urging), punching Donner in the testicles for good measure.
