Jesus’ mother and brothers probably believed, as in Mark 3:21, that he had lost his senses. John writes that his brothers did not believe in him (John 7:3–5), and it seems that even Mary felt that he had gone too far (see Matthew 10:34–37), so Mary and her sons probably came to speak with Jesus about private matters, maybe even to restrain him from his work (Mark 3:21).
The reason Jesus’ mother and brothers came to him here in Matthew 12:46 was likely the same as in Mark 3:21: that they thought he had lost his senses. John also writes that his brothers did not believe in him (John 7:3–5). It appears that even Mary felt he had gone too far (see Matthew 10:34–37). At this time, Jesus’ brothers also did not yet believe in him (John 7:5). There is therefore every reason to assume that Mary and her sons came from Nazareth to speak with Jesus about private matters—or perhaps even to restrain him from his work (Mark 3:21).1
46 Comme Jésus s'adressait encore à la foule, voici, sa mère et ses frères, qui étaient dehors, cherchèrent à lui parler.