Mark 3 ends with the arrival of Jesus’ family to “rescue” Him from Himself. When the people tell Jesus that His mother and brothers are outside waiting for Him, He takes the opportunity to teach a significant point by asking a question: “Who are My mother and brothers?”
Then, Jesus teaches the people about the Kingdom by way of parables. He teaches this way so that even our understanding of the Kingdom is by grace and not by anything in us. It must be given to us from above.