You can describe a man as your brother if he belongs to the same race, religion, country, or profession as you, or if he has similar ideas to you.
弟兄 (用于指同一种族、宗教、国家、职业或有相同思想的人)
Oh, so you're Peter's younger brother.
噢,这么说你是彼得的弟弟。
...the film company Warner Brothers.
华纳兄弟影业公司