You can say that you are not your brother's keeper to indicate that you do not accept responsibility for other people in any way. Part of me wants to help him, but part of me realizes I can't be my brother's keeper. Note: These expressions come from a story in the Bible. Cain has killed his brother, Abel, but tries to deny it. `And the Lord said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother's keeper?' (Genesis 4:9)