We find one of the most important connections in Luke 1:36 Luke 1:36And, behold, your cousin Elisabeth, she has also conceived a son in her old age: and this is the sixth month with her, who was called barren.
American King James Version×, where the same angel who informs Mary that she will bear a Son also tells her, "Elizabeth your relative has also conceived a son in her old age." This same Elizabeth would give birth to a son named John, who would be known to history as John the Baptist (Luke 1:57-60 Luke 1:57-60  Now Elisabeth's full time came that she should be delivered; and she brought forth a son.  And her neighbors and her cousins heard how the Lord had showed great mercy on her; and they rejoiced with her.  And it came to pass, that on the eighth day they came to circumcise the child; and they called him Zacharias, after the name of his father.  And his mother answered and said, Not so; but he shall be called John.
American King James Version×, Luke 1:80 Luke 1:80And the child grew, and waxed strong in spirit, and was in the deserts till the day of his showing to Israel.
American King James Version×).
The exact relationship between Mary and Elizabeth isn't spelled out, but apparently they were cousins, which made Jesus and John cousins. The two of them were clearly aware of each other's ministries, and when John saw Jesus coming to him to be baptized, he exclaimed, "Behold! The Lamb of God who takes away the sin of the world!" (John 1:29 John 1:29The next day John sees Jesus coming to him, and said, Behold the Lamb of God, which takes away the sin of the world.
American King James Version×).
While it was divinely revealed to John that his cousin Jesus was the prophesied Messiah (John 1:30-34 John 1:30-34  This is he of whom I said, After me comes a man which is preferred before me: for he was before me.
 And I knew him not: but that he should be made manifest to Israel, therefore am I come baptizing with water.
 And John bore record, saying, I saw the Spirit descending from heaven like a dove, and it stayed on him.
 And I knew him not: but he that sent me to baptize with water, the same said to me, On whom you shall see the Spirit descending, and remaining on him, the same is he which baptizes with the Holy Ghost.
 And I saw, and bore record that this is the Son of God.
American King James Version×), the fact that John so unhesitatingly accept-ed the truth of this revelation testifies to the fact that Jesus had to have lived a sinless and upright life.
Some apostles were cousins
Although few people are aware of it, at least two of Jesus' apostles also apparently were cousins. We discover this when we compare the lists of the four women who witnessed Jesus' crucifixion as recorded in Matthew 27:56 Matthew 27:56Among which was Mary Magdalene, and Mary the mother of James and Joses, and the mother of Zebedees children.
American King James Version×, Mark 15:40 Mark 15:40There were also women looking on afar off: among whom was Mary Magdalene, and Mary the mother of James the less and of Joses, and Salome;
American King James Version×and John 19:25 John 19:25Now there stood by the cross of Jesus his mother, and his mother's sister, Mary the wife of Cleophas, and Mary Magdalene.
American King James Version×. Comparing these accounts we see that the women included:
• Mary of Magdala or Mary Magdalene (mentioned by Matthew, Mark and John);
• Mary, the mother of Jesus (mentioned by John);
• Another Mary, identified by John as "Mary wife of Clopas" and by Matthew and Mark as "Mary the mother of James and Joses."
This James is generally identified as James the Less, one of the 12 apostles, also called "James the son of Alphaeus" (Matthew 10:3 Matthew 10:3Philip, and Bartholomew; Thomas, and Matthew the publican; James the son of Alphaeus, and Lebbaeus, whose surname was Thaddaeus;
American King James Version×; Mark 3:18 Mark 3:18And Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and Simon the Canaanite,
American King James Version×; Luke 6:15 Luke 6:15Matthew and Thomas, James the son of Alphaeus, and Simon called Zelotes,
American King James Version×). "Clopas" and "Alphaeus" seem to be variations of the Aramaic name "Chalphai," which can be transliterated into Greek as "Clopas" and Latin as "Alphaeus."
The 2nd-century historian Hegesippus states that Clopas was a brother of Joseph, Mary's husband and stepfather of Jesus. If true, then this apostle James was a cousin of Jesus.
• Salome (mentioned by Mark), also called "the mother of Zebedee's sons" by Matthew and "His [Jesus'] mother's sister" by John. With Salome and Mary being sisters, their children—Jesus, son of Mary, and the disciples James and John, sons of Salome and Zebedee—were first cousins.
This relationship sheds light on the incident in Matthew 20:21 Matthew 20:21And he said to her, What will you? She said to him, Grant that these my two sons may sit, the one on your right hand, and the other on the left, in your kingdom.
American King James Version×, where "the mother of the sons of Zebedee" asked that her sons, James and John, be given the two most prominent positions in Christ's Kingdom. The request seems quite audacious—but then we realize that the requester was Jesus' aunt, making the request on behalf of His two cousins.
Their closeness to Jesus as family members likely made them think such a request wouldn't be seen as too forward—and also helps explain Jesus' tactful but firm response.
This family relationship also helps us understand why James and John, along with Peter, were the three disciples Jesus seems to have been closest to, asking them to accompany Him at significant times and events (Matthew 17:1-9 Matthew 17:1-9  And after six days Jesus takes Peter, James, and John his brother, and brings them up into an high mountain apart,
 And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light.
 And, behold, there appeared to them Moses and Elias talking with him.
 Then answered Peter, and said to Jesus, Lord, it is good for us to be here: if you will, let us make here three tabernacles; one for you, and one for Moses, and one for Elias.
 While he yet spoke, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear you him.
 And when the disciples heard it, they fell on their face, and were sore afraid.
 And Jesus came and touched them, and said, Arise, and be not afraid.
 And when they had lifted up their eyes, they saw no man, save Jesus only.
 And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead.
American King James Version×; Matthew 26:36-37 Matthew 26:36-37  Then comes Jesus with them to a place called Gethsemane, and said to the disciples, Sit you here, while I go and pray yonder.  And he took with him Peter and the two sons of Zebedee, and began to be sorrowful and very heavy.
American King James Version×; Mark 5:37 Mark 5:37And he suffered no man to follow him, save Peter, and James, and John the brother of James.
American King James Version×). Jesus was evidently close to these two cousins in particular, and obviously enjoyed their companionship. It isn't much of a stretch of our imagination to think they might have grown up together and been friends from childhood.
Jesus' brothers and sisters
The Gospels also show us that Jesus had many half brothers and half sisters who were born to Joseph and Mary. In Matthew 13:55-56 Matthew 13:55-56  Is not this the carpenter's son? is not his mother called Mary? and his brothers, James, and Joses, and Simon, and Judas?
 And his sisters, are they not all with us? From where then has this man all these things?
American King James Version×we see that some residents of Nazareth asked: "Is this not the carpenter's son? Is not His mother called Mary? And His brothers James, Joses, Simon, and Judas? And His sisters, are they not all with us?"
This passage names four half brothers —Jacob, Joseph, Simeon and Judah in Hebrew—and mentions His half sisters (plural). Thus Jesus had at least six half siblings—four brothers and two sisters.
During Jesus' life, His half brothers did not believe in Him as Savior and Messiah (John 7:5 John 7:5For neither did his brothers believe in him.
American King James Version×). Yet, after His resurrection, James became a prominent believer. In Acts 1:14 Acts 1:14These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brothers.
American King James Version×James, along with his other brothers and his mother Mary, is among the original members of the Church, the same group that received God's Spirit on the day of Pentecost (Acts 2:1-4 Acts 2:1-4  And when the day of Pentecost was fully come, they were all with one accord in one place.  And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.  And there appeared to them cloven tongues like as of fire, and it sat on each of them.  And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
American King James Version×).
James later became a leader of the Jerusalem congregation. He played a prominent role in the conference of Acts 15 (see Acts 15:13-21 Acts 15:13-21  And after they had held their peace, James answered, saying, Men and brothers, listen to me:
 Simeon has declared how God at the first did visit the Gentiles, to take out of them a people for his name.
 And to this agree the words of the prophets; as it is written,
 After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up:
 That the residue of men might seek after the Lord, and all the Gentiles, on whom my name is called, said the Lord, who does all these things.
 Known to God are all his works from the beginning of the world.
 Why my sentence is, that we trouble not them, which from among the Gentiles are turned to God:
 But that we write to them, that they abstain from pollutions of idols, and from fornication, and from things strangled, and from blood.
 For Moses of old time has in every city them that preach him, being read in the synagogues every sabbath day.
American King James Version×). Paul later visited James in Jerusalem (Acts 21:18 Acts 21:18And the day following Paul went in with us to James; and all the elders were present.
American King James Version×). In Galatians 2:9 Galatians 2:9And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given to me, they gave to me and Barnabas the right hands of fellowship; that we should go to the heathen, and they to the circumcision.
American King James Version×Paul refers to James as a "pillar" of the Church. James also wrote the New Testament epistle that bears his name (James 1:1 James 1:1James, a servant of God and of the Lord Jesus Christ, to the twelve tribes which are scattered abroad, greeting.
American King James Version×). Another brother listed above, Judas or Judah (Matthew 13:55 Matthew 13:55Is not this the carpenter's son? is not his mother called Mary? and his brothers, James, and Joses, and Simon, and Judas?
American King James Version×), wrote the short epistle of Jude (Jude 1:1 Jude 1:1Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called:
American King James Version×).
The fact that these relatives, including half brothers who grew up with Him under the same roof, accepted Jesus as Messiah and personal Savior is also strong testimony to fact that He lived an exemplary and sinless life. And the fact that they became believers after His resurrection is a powerful witness to the reality of that resurrection from the grave.