In short
Jesus does not refer to the crowd as a whole, but calls his disciples his true relatives: his brothers… in the midst of the congregation
(Hebrews 2:11). Every believer is part of his spiritual family—closer to him than his kin by blood.
In Matthew 12:49, Jesus does not turn to the crowd as a whole, but specifically to those whom he identifies as his true relatives. In his work as Mediator, Jesus is most closely bound to his spiritual family (Hebrews 2:11).1 Jesus sees every believer as part of this family. His followers stand nearer to him even than his earthly kin. Indeed, even more: his disciples take the place of his earthly family.2
49 And stretching out his hand toward his disciples, he said, “Here are my mother and my brothers!