Jesus has obviously been causing some commotion in town, what with the Pharisees stalking him and accusing him of having a demon while the multitudes clamor for another miracle. It has reached the point of causing embarrassment to his family. Perhaps at the urging of neighbors and friends, his mother and brothers all decide to team up, seek Jesus out, and tell him to knock it off.
That's why they arrive at the place where Jesus is teaching, someone's house perhaps, but instead of going in they send someone inside to call Jesus out. They stand apart from the gathering, refusing to be a part of it. They do not want to confront Jesus publicly and embarrass him or themselves. Let him come out and talk to us. So there they stand, waiting. They have arrived as a group to show Jesus that they've discussed this, they stand together as a family, and they have all agreed that he has gone off his rocker. Now won't you please listen to Mother and come home this instant?
Like any good son--and you have to believe that Jesus is the best son that has ever lived--he loves his mother. He loves his brothers too, and his sisters, and their spouses and children. So you cannot gloss over how painful this situation must be for him, the public disapproval of his own family, clearly ashamed of him, demanding that he call off the apparent charade. We know you. We're your family. You don't impress us like you've impressed these other people. We've been patient with you but now you've gone too far. Don't make us come in there and get you.
Under the pressure of the situation Jesus responds as a dutiful son should . . . to his Father. Jesus does not bend to the will of Mary his earthly mother--despite what the Roman Catholic Church teaches--but to God his heavenly Father. His Father has many children, all of whom sit at Jesus' feet in that very house, all of whom are ready to do the will of God whatever the cost. By being where he is, Jesus is being true to his family. He would not shame or disappoint them by forsaking them for the passing pleasures of this life. And he gives comfort to those of us who have made similar sacrifices, that even if we are rejected by our earthly families, we have mothers and brothers and sisters in our heavenly family, Jesus as our Elder Brother and God as Father of us all.