stepbrother

A son of one’s stepparent.

One’s stepfather’s or stepmother’s son by a former marriage.

A brother by the marriage of one’s father with the mother of another, or of one’s mother with the father of another.

The son of one’s stepfather or stepmother who is not the son of one’s mother and is not the son of one’s father.

The stepson of one’s father or mother which is not one’s half-brother.

a brother who has only one parent in common with you