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Undoubtedly, the time will come when you and I will have to give an account to God of the way we treat our brothers; not only the blood brothers, but also the brothers of faith in Christ.
In the book of Genesis, we find an episode that evidences what was mentioned in the previous paragraph.
Genesis 4: 9 King James Version (NIV)
9 And Jehovah said to Cain, Where is your brother Abel? And he replied: I don't know. Am I my brother's guardian?
The theme of brotherhood arises early in Scripture, and from the beginning it is clear that God attaches importance to fraternal relationships. In this passage the question of the responsibility of one towards the other appears for the first time. Cain asks: "Am I my brother's guardian?" The word used for "guardian" (from the Hebrew Shamar) means "safeguard, protect, assist or consider." We are responsible? "Certainly," is God's answer. Not only are we guardians of our brothers and sisters, but we will be called to trial for our treatment of our brothers and sisters (physical and spiritual).
Because of Cain's sins against his brother, God curses him, takes away his ability to cultivate him and condemns him to a life of a fugitive and wanderer (Verse 12). This clearly indicates that the lack of fraternal harmony destines us to sterility and frustration in our purposes.
@elpastor, God gives very important importance to fraternal harmony and we are really called not only to love and take care of our blood brothers but also spiritual ones, because this attitude really honors God.
@ ricci01.