Brother (noun)

1. A son of the same parents as oneself.
2. A man who shares a common ancestry, culture, or interest with another.
3. A fellow member of a male religious order.

Origin:

Old english brōþor, of germanic origin; related to dutch broeder and german bruder, also to breed.

Examples:

1. He's my younger brother.
2. The two brothers have been inseparable since childhood.
3. She found a new sense of purpose when she joined a religious order and met her spiritual brothers.
4. The soldiers fought as if they were brothers.
5. The United States and Canada are close political and economic partners and are often referred to as brothers.