The Bible seems to clearly state that Jesus had siblings in various Gospel passages referring to his brothers and sisters, but there are other theories, as this article explains:
"Some have theorized that Jesus did not have brothers and sisters who were born to Mary and Joseph after His incarnation. In the article, ‘Did Jesus Really Have Half-Siblings?’, David A. Croteau writes, ‘Three views emerged in early church history. First, that the brothers and sisters of Jesus were children of Mary and Joseph after Jesus was born (referred to as the Helvidian view). Second, that they were children of Joseph from a prior marriage to Mary (referred to as the Epiphanian view). Third, that they were first cousins of Jesus (the traditional Roman Catholic view).” Croteau goes on to argue that, “It is striking that nowhere in the New Testament, or the first two centuries of Christianity, are they referred to as Jesus’ cousins.’”
Which view do you take? And perhaps more importantly, does it truly matter for our faith whether Jesus had biological half-siblings or not? Or is this actually more of a discussion about biblical interpretation and accuracy?
It’s also interesting to think about Jesus having siblings because it’s a way that his humanity is seen. Many of us know what it’s like to have a sibling(s), and that sibling dynamic is such a fundamental human experience for so many of us. I know my life was greatly shaped by my three siblings growing up and continues to be to this day.
Matt 13 from the Amplified Bible:-53 When Jesus had finished these parables, He left there. 54 And after coming to [Nazareth] His hometown, He began teaching them in their synagogue, and they were astonished, and said, “Where did this Man get this wisdom and these miraculous powers [what is the source of His authority]? 55 Is not this the carpenter’s son? Is not His mother called Mary? And are not His brothers, James and Joseph and Simon and Judas? 56 And His sisters, are they not [living here] among us? Where then did this Man get all this [wisdom and power]?” 57 And they took offense at Him [refusing to believe in Him]. But Jesus said to them, “A prophet is not without honor except in his hometown and in his own household.” 58 And He did not do many miracles there [in Nazareth] because of their unbelief.
It is clear that Jesus had both brothers and sisters.
Going strictly by what is written in Scripture we do not have enough information to make a concrete, dogmatic statement about the precise relationship of Jesus with His siblings.
Early Christian tradition suggested that Jesus’ siblings were the children of Joseph from a previous marriage (i.e. Joseph was a widower). Christians have pointed to several key pieces of information which may hint at this possiblity.
The way Jesus’ siblings treat Him is not as an elder brother (if these had been the children of Joseph and Mary after Mary gave birth to the Lord) but rather they act superior–which one would expect of older siblings in a household.
Jesus entrusts His mother to the care of His disciple. This is strange, since why would Mary need one of Jesus’ disciples to care for her if she had her own children (apart from Jesus) to take care of her? As such many Christians have seen this as possible evidence that Jesus’ siblings were not Mary’s kids, but they were probably Joseph’s from a previous marriage.
In later traditions some Christians, especially in the West, proposed that perhaps Jesus’ siblings were cousins. The Greek word we translate as “brothers” has a slightly broader range of meaning and can, in theory, include all manner of very close kin, not just blood-siblings, but first cousins as well.
So we have at least three options, and Scripture itself doesn’t really give us enough information to make a definitive conclusion:
These were the children of Joseph and Mary after Jesus was born.
These were the children of Joseph from a previous marriage.
These were cousins or close kin, but not strictly “siblings” in the modern way we use the term.
Again, the Bible itself doesn’t give us enough information to make a final conclusion that we can claim dogmatically. So we simply don’t know. But all three of what I listed above are things different Christians have believed and currently believe. Largely depending on what tradition/denomination one is a part of.