Brotherhood goes beyond just sharing the same family name — it’s about loyalty, protection, and unshakable bonds that last a lifetime.
These expressions are often used not only for real brothers but also for close friends, teammates, and people who share a strong sense of trust and connection.
Idioms for Brother
1. Blood is thicker than water
Meaning: Family relationships are stronger than friendships or other bonds.
Usage:
We may fight all the time, but blood is thicker than water.
He stood up for his brother because blood is thicker than water.
2. Big brother
Meaning: A protective or guiding older male, often used for an older sibling or a mentor.
Usage:
He’s like a big brother to everyone on the team.
My big brother always looked out for me when we were kids.
3. Like brothers
Meaning: Very close friends who share a bond like siblings.
Usage:
They’ve known each other since childhood — they’re like brothers.
Even though we’re not related, we’re like brothers in every way.
4. Brother from another mother
Meaning: A close male friend who feels like a brother, though not related by blood.
Usage:
Jake’s my brother from another mother — we’ve been best friends since high school.
He’s not my real brother, but he’s definitely my brother from another mother.
5. My brother’s keeper
Meaning: Responsible for looking after or protecting one’s brother (or another person).
Usage:
He’s always been his brother’s keeper, making sure he stays out of trouble.
Sometimes I feel like I’m my brother’s keeper, always cleaning up his messes.
6. Close as brothers
Meaning: Extremely close relationship, like that of siblings.
Usage:
The two soldiers became close as brothers during the war.
We’ve been close as brothers since college — nothing can break that bond.
7. Bro code
Meaning: An informal set of rules among male friends, especially regarding loyalty and respect.
Usage:
You never date your friend’s ex — that’s part of the bro code.
They joked about the bro code but took it seriously when it came to loyalty.
8. Brother in arms
Meaning: Someone who shares a struggle, mission, or experience with you (often military or team-related).
Usage:
He’s my brother in arms — we went through basic training together.
They’re brothers in arms, fighting for the same cause.
9. Sworn brother
Meaning: A friend who is as close as family due to a deep vow or shared experience.
Usage:
We’ve been sworn brothers since we started this business.
They became sworn brothers after surviving that dangerous hike together.
10. Thicker than thieves
Meaning: Extremely close and loyal; sharing everything, including secrets.
Usage:
Those two are thicker than thieves — always together.
My brother and I are thicker than thieves; we never keep secrets.
11. Brotherhood of man
Meaning: The idea that all humans are part of one family and should treat each other kindly.
Usage:
He believes in the brotherhood of man and helps anyone in need.
The speech focused on peace and the brotherhood of man.
12. Brothers at heart
Meaning: People who share a deep emotional or moral connection, like brothers.
Usage:
We may not share the same blood, but we’re brothers at heart.
They’re brothers at heart — always there for each other no matter what.
13. Brotherly love
Meaning: Genuine affection and care between brothers (or among people).
Usage:
He showed true brotherly love by helping his sibling through tough times.
That’s what I call brotherly love — always putting family first.
14. Brotherly bond
Meaning: A strong emotional connection shared between brothers or close friends.
Usage:
The brotherly bond between them was unbreakable.
Even after years apart, their brotherly bond remained strong.
15. Brothers under the skin
Meaning: People who are different on the outside but similar in spirit or values.
Usage:
Despite their backgrounds, they were brothers under the skin.
They come from opposite worlds but are brothers under the skin when it comes to integrity.
16. Brotherhood of the road
Meaning: A sense of connection among travelers or those sharing similar journeys.
Usage:
Truck drivers share a brotherhood of the road, always helping each other.
In motorcycling, there’s a brotherhood of the road — we look out for one another.
17. My brother in Christ
Meaning: Used among Christians to refer to fellow believers as spiritual brothers.
Usage:
He’s not my real brother, but he’s my brother in Christ.
They treated each other like family — true brothers in Christ.
18. A brother’s keeper
Meaning: Someone who feels a moral responsibility to care for or protect his brother or friend.
Usage:
He acted as his brother’s keeper when things got tough.
I’ll always be my brother’s keeper, no matter where life takes us.
19. Fraternal bond
Meaning: A deep connection of loyalty and friendship, like that of siblings.
Usage:
Their fraternal bond was forged through years of shared struggle.
The fraternity was built on mutual respect and a strong fraternal bond.
20. A brother’s shadow
Meaning: Living under the influence or reputation of one’s brother.
Usage:
He spent years trying to step out of his brother’s shadow.
Being the younger sibling, she always felt stuck in her brother’s shadow.
21. Brothers till the end
Meaning: Loyal and supportive of each other for life.
Usage:
No matter what happens, we’re brothers till the end.
They promised to stay brothers till the end, through every victory and loss.
