46While he was still speaking to the crowds, his mother and his brothers were standing outside, wanting to speak to him. 47Someone told him, “Look, your mother and your brothers are standing outside, wanting to speak to you.” 48But to the one who had told him this, Jesus replied, “Who is my mother, and who are my brothers?” 49And pointing to his disciples, he said, “Here are my mother and my brothers! 50For whoever does the will of my Father in heaven is my brother and sister and mother.” (Matthew 12:46-50, NRSV)
Who is a brother or sister to Christ? Anyone who does the will of God. If you do the will of God then you are a part of Christ’s family.
Blood does not make a brother or sister but trust in the one true God and loving God and loving your neighbor.
That is the will of God.