Ok....
But it's unfounded that "brother" means "Mary's child."
In koine Greek, "brother" and "sister" are VERY loose, generic terms and by no means are limited to biological siblings. And the term is often used for a step or half brother/sister. These verses CANNOT be used to prove Mary had other children; one may hold they IMPLY such or PROBABLY indicate such (both going too far) but don't prove anything.
Reality: The Bible is silent on whether Mary had any other children. But there is Tradition, from as early as the late First Century, that she did not... and that the siblings mentioned are children of Joseph from an earlier marriage. Does Tradition prove anything? No, but it does show the views of very early Christians... early enough to have EASILY named children of Mary. Frankly, I don't think we know from the Bible or history if May had any other children.... and I can't for the life of me image why it matters, BUT I know very early Christians believed she did not (and they'd know better than me). BTW, this has NOTHING to do with whether She had intimate relationships with Joseph - the subject of a Dogma.
Mary did not remain a virgin. Being a wife to Joseph as they are made one flesh, the scripture testify Joseph knew her after the birth of Jesus.
Matthew 1:24 Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife: 25
And knew her not till she had brought forth her firstborn son: and he called his name Jesus. ~ KJV
Then you have this announcement.
Matthew 12:6 While he yet talked to the people, behold, his mother and his brethren stood without, desiring to speak with him. 47 Then one said unto him, Behold, thy mother and thy brethren stand without, desiring to speak with thee. 48 But he answered and said unto him that told him, Who is my mother? and who are my brethren? 49 And he stretched forth his hand toward his disciples, and said, Behold my mother and my brethren! 50 For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother. ~ KJV
Then you have this reference to His family by unbelievers that knew Him & His family.
Mark 6:2 And when the sabbath day was come, he began to teach in the synagogue: and many hearing him were astonished, saying, From whence hath this man these things? and what wisdom is this which is given unto him, that even such mighty works are wrought by his hands? 3 Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him. 4 But Jesus, said unto them, A prophet is not without honour, but in his own country, and among his own kin, and in his own house. ~ KJV
If you consider the warning to flee to Egypt, no other children were mentioned.
Matthew 2:13 And when they were departed, behold, the angel of the Lord appeareth to Joseph in a dream, saying, Arise, and take the young child and his mother, and flee into Egypt, and be thou there until I bring thee word: for Herod will seek the young child to destroy him. 14 When he arose, he took the young child and his mother by night, and departed into Egypt: 15 And was there until the death of Herod: that it might be fulfilled which was spoken of the Lord by the prophet, saying, Out of Egypt have I called my son. ~ KJV
If you consider the time when they were taxed before Jesus was born, no other children were mentioned.
Luke 2:1 And it came to pass in those days, that there went out a decree from Caesar Augustus that all the world should be taxed. 2 (And this taxing was first made when Cyrenius was governor of Syria.) 3 And all went to be taxed, every one into his own city. 4 And Joseph also went up from Galilee, out of the city of Nazareth, into Judaea, unto the city of David, which is called Bethlehem; (because he was of the house and lineage of David
5 To be taxed with Mary his espoused wife, being great with child. 6 And so it was, that, while they were there, the days were accomplished that she should be delivered. 7 And she brought forth her firstborn son, and wrapped him in swaddling clothes, and laid him in a manger; because there was no room for them in the inn...... 16 And they came with haste, and found Mary, and Joseph, and the babe lying in a manger. 17 And when they had seen it, they made known abroad the saying which was told them concerning this child. ~ KJV
There were no other children of Joseph from another wife. Joseph knew his wife after Jesus was born & He had brothers & sisters. Those who strain against it are probably scholars educated by sources believing Mary remained a virgin & yet somehow was a good wife to Joseph? The whole point of marriage is building a family. If God wanted Mary to remain a virgin, He would not have made them one flesh.