Thank you for the question on universal brotherhood, “What is said in the Bible about universal brotherhood?”
Here are two thoughts for one’s consideration on the Scriptural view on the universal brotherhood of mankind.
A. The u uniniversal brotherhood of humanity is that each person is created in the image and likeness of God (Gen. 1:26–27).
The Scriptures declares the uniqueness and commonality of each person in being created in the image and likeness of God. The significance of that is that most people based their worth or value of oneself or of others on physical appearance, physical position/status in life and or physical possession. It is not about what one has in life but about who one is in life. It’s because every person is made in God’s image and likeness that one is to love one another as oneself. Without the acknowledgement of the Creator God, humans will have the tendency to emphasize one’s distinctiveness from appearance, position, and or possession over others. Humans will compare themselves to others and when one compares, one will be better than the other. Thus from a Scriptural perspective, there is no one superior or inferior to others since every one is made in the image and likeness of God. That is the true bases of universal brotherhood.
B. The universal brotherhood of Christians is that each believer is redeemed by the blood of Jesus Christ to become a child of God (John 1:12, I John 5:6–12).
The second aspect of universal brotherhood of Christians is the centrality of Jesus Christ in the Christian faith. The core foundation that binds Christians together is their belief that Jesus Christ died for their sins and rose again on the third day (I Cor. 15:1–8).
Regardless whether one is a Christian in Africa, Asia, Australia, Europe, Middle East, South or North America, what binds Christians together is their belief about Jesus Christ. There are no racism, Jew or Greek, rich or poor, slave or free, man or woman, the pastor or the parishioner, the church practices or church size for every believer stands equally at the foot of the Cross and before the throne of God.
Galatians 3 says this, “So in Christ Jesus you are all children of God through faith, 27 for all of you who were baptized into Christ have clothed yourselves with Christ. 28 There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. 29 If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise” (A searchable online Bible in over 150 versions and 50 languages).
Christians are not immune from comparison with others or elevating oneself based on appearance, position, or possessions. It happens more than Christians or churches like to admit. There are no perfect Christians or perfect churches, but when goes to pray before God, this universal brotherhood of being in the image and likeness of God and in Christ Jesus becomes for a moment a reality for believers.
SUMMARY: According to the Scriptures, universal brotherhood is based on each person being made in the image and likeness of God and the centrality of Jesus Christ within the Christian faith, not on appearance, position in life nor possessions in life.
For more perspectives:
https://www.quora.com/What-is-said-in-the-Bible-about-universal-brotherhood