Matt 12:46-50 While He yet talked to the people, behold, His mother and His brethren stood without, desiring to speak with Him. Then one said unto Him, Behold, Thy mother and Thy brethren stand without, desiring to speak with Thee. But He answered and said unto him that told him, Who is My mother, and who are My brethren? And He stretched forth His hand toward His disciples, and said, Behold My mother and My brethren! For whosoever shall do the will of My Father, which is in heaven, the same is My brother, and sister, and mother. (Also see Mark 3:31-35; Luke 8:19-21)
Jesus continued teaching the Jews of Galilee, as well as all that came to hear Him from other provinces of the Jewish nation, including the Jewish leaders from the temple in Jerusalem. He taught them of the kingdom of God that was at hand, and confirmed its truths with miracles of healing. While He yet talked to the people, behold, His mother and His brethren stood without, desiring to speak with Him. Some bible scholars contend that the family members spoken of here were children of an aunt, which would make those referred to as "His brethren," in reality, His cousins. Although this was a common practice among the Jewish people, most students of the bible tell us that these relatives were actually Mary, the wife of Joseph, and their other sons, which, in the strictest sense of the word, would be half-brothers to Jesus.
Other scriptures give us a good description of Jesus' immediate, earthly family. Both Matthew 13:55-56 and Mark 6:3 refer to Jesus as a carpenter and as the carpenter's son. They tell us that He was the son of Mary, and had brothers named James, Joses, Simon, and Judas. Although not named, these same texts tell us that Jesus also had a number of sisters. Jesus' mother and brothers accompanied Him on one of His first earthly preaching missions as He went down to Capernaum (John 2:12). Although we know little about most of Jesus' other brothers and sisters, the apostle Paul, when he visited Jerusalem, met with James the Lord's brother (Gal. 1:19). Certainly James, as a leader of the church of Christ in Jerusalem, believed with all his heart that his brother, Jesus, was indeed, the Son of God, and the promised Savior of the world. As a side note, I like the idea that Jesus' preaching and teaching took the form of talking to the people. He actually interacted with His audiences rather than lecture them without any consideration for their various needs and their differing abilities to comprehend the things He taught. This is a method of imparting the will of God to others that I feel would probably be more receptive to those desiring to know the truths of the gospel of Christ than the overpowering sermons that ridicule and condemn those living in sin.
Back to the lesson, we are not told exactly why Jesus' mother and brothers desired to speak with Him. Whether they were seeking a better understanding of the promised kingdom that He would establish, or whether they were concerned for His safety among the threats of the Jewish leaders, or for some other reason, we are not told. However, when it was brought to His attention that they were in His audience and desired to speak to Him, He used the occasion to demonstrate the most important relationship one can ever experience during their life on earth. Jesus replied with this question: Who is My mother, and who are My brethren? No doubt Jesus had a special, extremely strong affection for His mother and his brethren. This answer did not diminish from His deep love for all members of His physical, earthly family. However, as an important lesson for all of His followers at that time, and as an example to all Christians today, Jesus says that there is a spiritual family relationship that is far more precious than one's earthly family.
Jesus demonstrated this when He stretched forth His hand toward His disciples, and said, Behold My mother and My brethren! In numerous places in God's word, including Matthew 15:4, we are told to honor our father and mother. However, there is greater honor in the sight of God when one is obedient to His will, repents of their past sinful life, accepts and confesses His Son, Christ Jesus as their Savior, and is baptized for the remission of sins. God will then add them to His family; they become His children and joint heirs with Christ having the promised hope of eternal salvation and a home in heaven where we have the honor of living with Him, praising Him, and worshiping Him forever. No earthly family can offer such a great reward. Seek the family of God, become a part of it, and rejoice forever more!