Nope, no stretch. There are only four brethren of Jesus named in the Gospels: **Matthew 13:55 ** “Is not this the carpenter’s son? Is not His mother called Mary, and His brothers, James and Joseph and Simon and Judas?”
Mark 6:2-3 ** - "Is not this the carpenter, the son of Mary, and brother of James, and Joses, and Judas, and Simon? Are not His sisters here with us?"
Let’s begin with James. There are two men named James among the disciples. One, of course, is the brother of John and the son of Zebedee. This cannot be him then. So, this is the other James, called in Scripture James the less: Mark 15:40: "There were also women looking on afar off: among whom were Mary Magdalene, and ** Mary the mother of James the less, and of Joseph, and Salome." (emphasis added)
So James is indeed the son of a woman named Mary. Not only that, but Joseph is his brother. That’s two of the four, right? Then, in Matthew, reciting the names of the twelve: Matt 10:3: “…'James the son of Alphaeus, and Lebbaeus, whose surname was Thaddeus.” (emphasis added)
This too is talking of James the less, as the other James, son of Zebedee, is spoken of in the previous verse. It is NOT a trick or really that hard! * Alphaeus* is this James’ father, not Joseph, the husband of Mary, mother of the Lord.
Now go to John also speaking of those witnessing the Crucifixion: John 19:25: “Now there stood by the cross of Jesus His mother (Mary) and His mothers sister, *** Mary the wife of Cleophas***, and * Mary Magdalene*.” (emphasis added)
Look up John 19:25 at blueletterbible.org/ and click the ‘C’ icon (for the Strong’s Concordance), then click the Strong’s number for the name Cleophas. It comes up “father of James the less, the husband of Mary the sister of the mother of Jesus.”
Did you get that? That Mary, who was the mother of James the less, and of Joseph, from Mark 15:40, is the wife of Cleophas, the father of James the less, and she is called the ‘sister’ of Our Lord’s mother - Mary!
So, two of the four ‘brothers’ have been identified as the children of parents other than Joseph and the Virgin Mary. Of the brothers named, that still leaves Jude and Simon. Next, Jude: Acts 1:13 ** "…James, the son of Alphaeus , and Simon Zelo’tes, and ** Jude the brother of James…" (emphasis added)
There goes Jude out of the mix! *** Matter of fact, Jude says the same in his own epistle: Jude 1:1 "Jude, a servant of Jesus Christ *** and brother of James…" (emphasis added)
Lastly, Simon. Simon, called the Zealot, is identified as coming from Cana, not Nazareth as were Joseph, Mary and the Christ! Luke 6:15 "and Matthew, and Thomas, and James the son of Alphaeus, and ** Simon who was called the Zealot," (emphasis added)
Mark 3:18 “Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphaeus, and Thaddaeus, and ** Simon the Cananaean**…” (emphasis added)
Matt 2:23 And he came and dwelt in a city called Nazareth: that it might be fulfilled which was spoken by the prophets, He shall be called a Nazarene. (emphasis added)
Simon is a Cananean, while Jesus is a Nazarene!
We see that Simon the Zealot being from Cana, and a ‘brethren’ or ‘brother’ of the Christ. Let’s go to John’s Gospel, chapter 2. Mary and Our Lord are invited to a wedding there! So, close business associates, maybe, of Joseph from the carpentry trade, or more likely - family, or brethren, relatives, are having this wedding! Like, maybe the Holy Family had actual kinfolk in Cana, be they cousins, in-laws, nephews, aunts, uncles, all of which are routinely called ‘brethren’!
Remember what Mary said to the servants? She told them to ‘Do as He says.’
Think about that a second? What would give this humble woman from Nazareth any position to so speak to the servants of someone else in an entirely different town, at their wedding? The simplest and most easily understood answer would be – she is a family relation to those giving the wedding feast…
So Simon is from Cana, and a ‘brother’ of the Lord! He’s not a sibling though, but very likely related. And James, Joseph and Jude all have the same father and mother, and it is not Joseph and the Virgin Mary, but their mother is named Mary and called the sister of Jesus’ mother Mary. Even here ‘sister’ may not mean blood sibling, or we have two sisters with the same name in the same family.