William can always rely on his brother when he needs help with something.
When a person’s mother or father remarries and has children who are male, there are a few different ways to refer to them. A step-brother is a male who is unrelated by blood. A half-brother is related through the mother or the father.
Jeremy has two step-brothers who are much older than he is. His father married their mother.
Veronica has a half-brother. Her mother married another man and they had a child together.
The word "brother" is often used figuratively when describing a man who has a feeling of kinship with other people:
Mario and Pablo have known each other for so long, they almost feel as though they are brothers.
Brett feels a sense of responsibility to help his Iraqi brothers with whom he fought during the war.
Hey, brother. Can you spare a dime?
The word "brotherhood" is used when men share common experiences and interests:
A brotherhood develops among police officers who have worked together for many years.
Malcom X believed in the brotherhood of man (this would include women).
Having survived five years in prison, the men still had a strong sense of brotherhood decades after their release.
Sometimes you’ll hear the word "brother" used when a person expresses frustration or dissatisfaction with a situation:
Oh brother! How long is this going to take?
There’s not going to be a concert because someone stole all of the microphones! Oh brother!
A shortened form of this word is "bro." This usage originated among African Americans, but now it’s fairly popular among many young Americans, regardless of race or ethnicity. (I don’t recommend that you use "bro" unless you feel comfortable using it.)