What does Matthew 12:50 mean?

Those hearing Jesus' words are being taught an expanded view of what true "family" is. He is inside a very crowded house teaching when He gets the news that His mother Mary and His brothers are waiting to speak to Him outside. Instead of going out to see them, Jesus points to His disciples and says, "Here are my mother and my brothers!" This is meant to make an important point (Matthew 12:46–49).

Christ defines His family through the connection to His Father in heaven—not to His earthly mother and brothers. He expands the idea of His family to be "whoever does the will my Father in heaven." He calls those people his brother and sister and mother. Eventually, at least some of Jesus' immediate earthly family will become part of this spiritual group (Acts 1:14).

Since this time, the church—all who trust in Christ and do God's will—has been described as a family. Believers are brothers and sisters in Christ because we all share the same Father in heaven. That Father has literally adopted us as His own children through our faith in Christ (Romans 8:15). That sense of belonging, the idea that the people of Christ are joined together by the bonds of family community, is central to being a Christian. None of us are alone.

In this moment, Jesus stresses that the unifying factor of spiritual "family" is doing the will of God the Father.