There are two passages in the gospel describing one event that is often used to show that Christian relationships must take priority over physical family relationships.
While he was still speaking to the people, behold, his mother and his brothers stood outside, asking to speak to him. But he replied to the man who told him, “Who is my mother, and who are my brothers?” And stretching out his hand toward his disciples, he said, “Here are my mother and my brothers! For whoever does the will of my Father in heaven is my brother and sister and mother.” (Matthew 12:46-50, ESV)
Then his mother and his brothers came to him, but they could not reach him because of the crowd. And he was told, “Your mother and your brothers are standing outside, desiring to see you.” But he answered them, “My mother and my brothers are those who hear the word of God and do it.” (Luke 8:19-21, ESV)
In the Western, individualistic, modernist culture, where we tend to think in either-or terms, we read Jesus seeming to say that a Christian must choose to prioritize either physical familial relationships or the spiritual relationship that s/he enters into upon acceptance of Christ as Lord.
But is there an alternative interpretation that may be more faithful to the culture and intent when the words were spoken? What might an ancient Middle Eastern, collectivist culture have heard in Jesus’ words? What if we took a both-and stance instead of either-or? E. Randolph Richards (M.Div. and Ph.D., Southwestern Baptist Theological Seminary) and Brandon J. O’Brien (M.A., Wheaton College Graduate School), in Misreading Scripture With Western Eyes writes,
The non-Western concept of family is broader than the Western. But Jesus expanded it even more. For Jesus, family not only designated one’s immediate, biological relatives but included all who are knit together in faith. Once while Jesus was teaching in someone’s home, a messenger told him his mother and brothers wanted to speak with him. Jesus pointed to his disciples and said, “Here are my mother and my brothers. For whoever does the will of my Father in heaven is my brother and sister and mother” (Mt 12:49-50). This is a radical statement in a culture in which birth determines your family.
What Richards and O’Brien are telling us is that Jesus didn’t say that a spiritual family takes precedence over the biological, or that the more genuine family is a spiritual one; but rather, the definition of family now includes both biological and those who join in through a spiritual, faith relationship.
 Misreading Scripture With Western Eyes: Removing Cultural Blinders to Better Understanding the Bible. Kindle edition, location 1114.