Brotherly love is from God

"If you see your brother's donkey or his ox fallen in the way, you shall not turn away from it; you shall help him to lift it up." Deuteronomy 22:4

In this text, God wants to teach us about solidarity, brotherhood and love. Of course, there are many other teachings as well.

By solidarity, we mean the feeling that drives people to give each other mutual help because community life demands it. "Let each of you, instead of considering his own interests, also consider those of others." (Philippians 2:4)
By fraternity, we are committed to a close relationship that obliges us to live as brothers. "They persevered in the apostles' teaching, in fellowship, in the breaking of bread, and in prayer." (Acts 2:42)

As for love, it's a deep affection for someone or something (belonging to a brother). Love implies the two characteristics mentioned above, brotherhood and then solidarity. "Love does no harm to a neighbor: therefore love is the fulfillment of the law." (Romans 13:10)

"Moreover, brethren, rejoice, be perfected, be comforted, be of one mind, live in peace; and the God of love and peace will be with you." (2Corinthians 13:11)