1) Blood brother 2) Brother 3) Half-brother 4) Possible relative 
• (n.) A brother by the marriage of one`s father with the mother of another, or of one`s mother with the father of another.
Step'broth`er noun A brother by the marriage of one's father with the mother of another, or of one's mother with the father of another. 
[n] - a son of your stepparent by a former marriage
half-brother noun a son of your stepparent by a former marriage
one's stepfather's son or stepmother's son by a previous marriage.