(humble) siblings
Example sentences
彼は正直で働き者だが彼の兄弟は全く反対だ。
He is honest and hard-working, but his brother is the exact opposite.
彼は私の最も親しい友人で、言わば兄弟だ。
He is my closest friend; we are like brothers.
彼は私の兄弟より３才年下です。
He is junior to my brother by three years.