“There came then his brethren and his mother, and, standing without, sent unto him, calling him.”
King James Version (KJV)
3:31 Then come his brethren and his mother - Having at length made their way through the crowd, so as to come to the door. His brethren are here named first, as being first and most earnest in the design of taking him: for neither did these of his brethren believe on him. They sent to him, calling him - They sent one into the house, who called him aloud, by name. #Mt 12:46|; Lu 8:19.
Mr 3:31 There came then his brethren and his mother. See notes on Mt 12:46-50. Compare Lu 8:19. The natural inference is that the "brethren" were the sons of Mary and the half-brothers of Jesus. No other idea would ever have been maintained had it not been that the doctrine of the perpetual virginity of Mary arose some centuries after the apostles.