We had a hint of what was coming a couple readings earlier. Jesus’ mother and brothers came to get Him because they thought He was out of His mind (vs. 21). The placement of the previous reading about the Pharisees accusing Jesus of being demon possessed leads us to think that Jesus’ family was thinking the same thing about Him.
When they come for Him, Jesus ignores them, and asks the question “Who are my mother and my brothers?” Jesus isn’t saying that family relationships are not important, because they are very important. Jesus even appeared separately to His brother James after His resurrection. But one’s relationship to God is even more important than that of our family.
Who is this Jesus? He is the One who understands the priority of relationships, especially keeping our relationship to God as the most important.