But you're not sure, even though Scripture clearly states it.
Re: Jesus' brothers. The original Aramaic had no word for "brothers" as we know it.
What original Aramaic? Check the inscription on the cross for the languages spoken around Jerusalem: Latin, Hebrew, and Greek and the original Greek used the word "adelphos" meaning "blood brothers".
They were possibly cousins or step-sons (Joseph's children from a previous marriage.)
If that is the case then they were not related to Jesus in any way --- not brothers, not cousins, not kinsmen, not relatives at all. And they would also have been older, so were they there in the stable in Bethlehem? Where were they when the magi stopped by? Did they travel with them to Egypt? Were they staying with the ex-wife for the weekend?
The Bible does NOT clearly state that Mary had other children.
If Jesus had brothers and sisters, as Scripture states, they had to be Mary's children, because she was the only parent whose DNA they shared.
In fact, if she had, why did Jesus, when he was hanging on the cross, tell John that he was now Mary's son and that Mary was his mother and that from that day forth he took her into her home? If Mary had had other children, she would have been living with them, not John.
Looking after the surviving parent was the responsibility of the oldest son, and Jesus is taking care of his responsibilities to the bitter end, and not passing them on in absentia to a younger sibling who may not have been prepared to accept that responsibility.
Re: "Man does not live by bread alone, but by every word that comes from the mouth of God." Jesus is the Word. He is God. He is also the Living Bread. "I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world." John 6:51
So you interpret this passage literally, but the passages regarding the brothers of Jesus as the children of Mary figuratively? How do you know when to interpret literally and when to interpret figuratively?
Aramaic was what Jesus and everybody else spoke. His last words on the cross were Aramaic: "Eloi, Eloi, lama sabachthani?" (Mark 15:34) I've already explained that there was no Aramaic word for "brothers," only "kinsmen." The people called Jesus' "brothers" most definitely could have been cousins, second cousins or whatever on Mary's side and also on Joseph's side, because since they were married his kinsmen were her kinsmen. Remember the words of Ruth to Naomi that Naomi's people would be her people and her God Ruth's God, simply because Naomi was her mother-in-law?
This has me still chuckling.
In fact, if she had, why did Jesus, when he was hanging on the cross, tell John that he was now Mary's son and that Mary was his mother and that from that day forth he took her into her home? If Mary had had other children, she would have been living with them, not John.
The reason Jesus gave the care of his mother to his cousin, John, was the animosity he and his own brothers had between each other [Mark 3:21]. Here they call him crazy. [Mark 3:31-35] Here, he publicly rebukes them. And the same here [Luke 19-21]. Here, his own brothers want him killed (at the hands of the Jews) [John 7:1-5] and "they did not believe in him". This would have been very strange if "These" brothers were only brothers in spirit, camp followers or disciples....would it not? No, they were flesh and blood, sons of Joseph and Mary....and very jealous of Jesus and his miracles (verse 3).