From Longman Dictionary of Contemporary Englishstepbrotherstep‧broth‧er /ˈstepbrʌðə $ -ər/ noun [countable] SSFFAMILYthe son of your stepmother or stepfather
Examples from the Corpus
stepbrother• I have five and a half stepbrothers and sisters.• Shari struggles against her passionate feelings for her stepbrother.• Was it possible her friend had been matchmaking - her stepbrother and her best friend?• Caro said her stepbrother was Robert Marsh the naturalist.• Your son resents his stepbrother for taking up your time, and is worried that you don't love him any more.• His stepbrother, half-scandalized and wholly impressed by Herbert's levity, never forgot the episode.• Some of them even had to endure the presence of stepbrothers and -sisters, which to Camille would have been insupportable.• The notion that Caro's stepbrother was called something totally different niggled at her. 