stepbrother
/ˈstɛpˌbrʌðər/
noun
- The son of one's stepparent (the person a parent married after divorce or death), who is not biologically related to oneself.
- My stepbrother and I get along really well, even though we didn't grow up together.
- She introduced her stepbrother at the family reunion.
- After his mother remarried, he gained a stepbrother who was the same age.