One time Jesus said, “A man's foes shall be they of his own household.” (Matt 10: 36) At another time he said, “Whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother.” (Matt 12:49-50) These can be viewed as interesting comments, considering the makeup of the group most closely associated with him.
We often think of the apostles as twelve individuals with little in common besides a devotion to Jesus. We tend to forget the family ties among these twelve men. Most people remember that Peter and Andrew were brothers. Of course we remember that James and John were brothers; they were the sons of Zebedee. Some may even remember that those four were business partners. (Lk 5:10) Beyond that we generally look at these men as unrelated. It is possible, however, that there were other relatives in the group.
When Matthew introduces himself it is as “Levi bar (son of) Alphaeus.” Another of the apostles is always called “James bar Alphaeus.” Now it is entirely possible that these two had separate fathers who shared a common name. Considering that Jesus had also selected two sets of brothers, it is just as likely that these two were brothers.
Thomas is called “the twin.” None of the other apostles is specifically called a twin, but it may be that the twin brother of Thomas was also among the twelve. In the lists of the apostles, Thomas is twice listed with one called the son of Tolmai (Bartholomew in English), who is probably also called Nathanael. In John 21 a number of disciples were together. Those mentioned by name are Peter, James and John, Nathanael and Thomas. Because of these close associations it is likely that Thomas the Twin and Nathanael were Thomas and Nathanael bar Tolmai.
One apostle, called variously Lebbaeus, Thaddeus, or Jude (Judas), is called the brother of James. James is a common name, but because it is singled out here he was likely the brother of a specific James that was known to those to whom Luke wrote. It is possible, but unlikely, that he was brother to the sons of Zebedee. He might be brother to the other apostle James, which might make him brother to Matthew, but Matthew gives no hint of such a relationship. The other well-known James in Luke’s writings is James the son of Mary. This is the most likely James to whom Luke relates Jude. That would mean that one of the brothers of was also one of his apostles. Although the scriptures mention his family doubting Jesus, it is still a strong possibility that he had a physical brother among the apostles.
Nor is this last speculation too farfetched, when others have speculated that he also had a cousin among the twelve. In the descriptions of the crucifixion and burial of Jesus, three accounts list three women who were present. Mark 15:40 lists them as “Mary of Magdala, Mary the mother of James the less and Joseph, and Salome.” Matthew lists “Mary of Magdala, Mary the mother of James and Joseph, and the mother of Zebedee’s sons.” John lists “Mary the mother of Jesus, her sister Mary wife of Clopas, and Mary of Magdala.” This has given rise to two theories. One is that Mary the wife of Clopas is Salome the mother of Zebedee’s sons. Mary the mother of James the less and Joseph would then be the mother of Jesus. That would make James and John cousins to Jesus. The other theory is that Salome is the wife of Zebedee, but Mary the mother of James the less is not the mother of Jesus but rather the wife of Alphaeus, father of James and possibly Matthew. That necessitates that Alphaeus is also known as Clopas. This theory says that only John mentions the mother of Jesus (thus making three Mary’s). That would make the apostles James bar Alphaeus and possibly Matthew Levi bar Alphaeus cousins to Jesus.
With so many relatives among his apostles it is indeed strange that Jesus would prophecy that brother would turn against brother. (Mk 13:12) But then, maybe he figured that such a prophecy would cause the brothers among the apostles to draw closer together so it would not happen to them.