Did Jesus really have brothers and sisters? Did any of his earthly family become Christians? Were any active in the New Testament church?
Mary and Elizabeth
How were Jesus' and John the Baptist's mothers related? Surprisingly, we can determine their family relationship entirely from the first chapter of Luke's gospel!
The Lineage of Elizabeth
There was in the days of Herod, the king of Judea, a certain priest of the course of Abijah, Zacharias by name; and his wife was of the daughters of Aaron, and her name was Elizabeth (Luke 1:5, HBFV throughout).
The course of Abijah was one of twenty-four devised by King David in order to allow the many Levites a chance to serve at the temple (1Chronicles 24). Zacharias, from the tribe of Levi, served at Jerusalem's temple during this course. Each course lasted one week which allowed the priests to serve at least twice in a given year. His wife Elizabeth was also from the tribe of Levi, specifically a descendant of Israel's first High Priest named Aaron.
The Lineage of Mary
Mary, through her father Heli, was of the tribe of Judah (Luke 3:23). Joseph, who was betrothed to her before the birth of Jesus, was also from Judah (Matthew 1:1 - 16).
The Relationship
The closing words of the angel Gabriel, sent by God to inform Mary she will miraculously give birth to Jesus, reveals the family relationship between her and Elizabeth.
Now behold, Elizabeth your kinswoman (Greek suggenes, Strong's #G4773) has also conceived a son in her old age; and this is the sixth month for her who was called barren (Luke 1:36).
Suggenes, translated as "kinswoman" above, is translated as "cousin" in the King James and "relative" in the NIV, NASB, HCSB and other translations. How could Mary and Elizabeth, however, be related to each other when their fathers were from two different Israelite tribes?
The Solution
Mary and Elizabeth were related to each other through their mothers! Their mothers were sisters produced by a couple who are unnamed in the Bible.
First cousins (or simply "cousins") are people who share a common grandparent. What are called "second cousins" are those who share a great-grandparent. In regard to Mary and Elizabeth, they were first cousins. This made their children, Jesus and his six half-siblings and John the Baptist, second cousins!
"Though Elisabeth (Elizabeth) was, on the father's side, of the daughters of Aaron (v. 5), yet on the mother's side she might be of the house of David, for those two families often intermarried . . ." (Matthew Henry's Commentary on the Whole Bible).
"Thy cousin Elisabeth (Elizabeth) . . . As Elisabeth was of the tribe of Levi, Luke 1:5, and Mary of the tribe of Judah, they could not be relatives but by the mother's side." (Adam Clarke's Commentary).
Before Consummation
Mary became pregnant with Jesus when she was betrothed to Joseph but before they had consummated their marriage (Luke 1:34, Matthew 1:18). Even after the miraculous conception the couple refrained from having sex until after the birth of Jesus.
And when Joseph was awakened from his sleep, he did as the angel of the Lord had commanded, and took his wife (Mary) to wed; But he did not have sexual relations with her UNTIL AFTER she had given birth to her Son, the firstborn; and he called His name Jesus (Matthew 1:24 - 25).
A Normal Marriage
The belief, held by some, that Mary was a "perpetual virgin" is contrary to sound Biblical teachings. Both her and her husband, sometime after the birth of Jesus, did consummate their marriage. They had sex like any normal couple at the time and from it produced a large family of four sons and (at least) two daughters.
The children Mary and Joseph produced were named James, Joseph, Simon, Judas (Jude) and at least two daughters. Those in their small hometown of Nazareth were well acquainted with the family and personally knew the children the couple produced.
From where did this Man (Jesus) receive this wisdom and these works of power? Is this not 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? . . . (Matthew 13:55 - 56).
Half-Brothers and Sisters
Other than a rare reference (Matthew 12:46, 13:55 - 56, Acts 1:14) nothing is revealed in the Bible about half-brothers Joses and Simon, as well as the half-sisters of Jesus. There is information, however, on family members James and Judas (called Jude).
James
The Apostle Paul mentions that James, Jesus' half-brother, was one of the last people to see him alive after his resurrection from the dead. Note that Paul, in the below verses, refers to him as an apostle.
And that He (Jesus) appeared to Cephas, and then to the twelve. Then He appeared to over five hundred brethren at one time, of whom the greater part are alive until now, but some have fallen asleep. Next He appeared to James; then to all the apostles . . . (1Corinthians 15:5 - 7).
There can be no doubt that James was a leader in the early New Testament church (Acts 12:11 - 17). He was the acknowledged head of the Jerusalem Conference which met to determine if circumcision should be required of Gentile converts (Acts 15).
The book of James, written by him, is the second earliest writing included in the New Testament. It was written between 40 to 41 A.D., just a few years before Matthew's gospel was penned in 35 A.D.
Jude
Jude (Judas), another half-brother of Jesus, was like James a leader in the early church.
Jude's book was one of the last ones written in the New Testament. His general epistle was recorded from 66 to 67 A.D., created before 2Timothy (67 A.D.) and the book of Revelation (c. 95 A.D.).
Are Descendants Alive Today?
Are there people living today who are in the family tree of Joseph and Mary, and hence partially related by blood to Jesus Christ? Given that the couple produced at least six children who were his half brothers and sisters, there is a possibility that there are some people living today who have a genetic link to Jesus and don't know it!