The Bible states that Mary had other children besides Jesus. That is sufficient for me. However Catholic tradition interprets the various phrases differently, brother = cousin, etc Surely if God wanted Mary to remain a virgin He could have done so. Who knows? We may never find out. Here are some key verses in question
Matthew 1:24-25 - “And Joseph arose from his sleep, and did as the angel of the Lord commanded him, and took as his wife, and kept her a virgin until she gave birth to a Son; and he called His name Jesus.”
Matthew 12:46-47 - “While He was still speaking to the multitudes, behold, His mother and brothers were standing outside, seeking to speak to Him. And someone said to Him, “Behold, Your mother and Your brothers are standing outside seeking to speak to You.”
Matthew 13:55 - “Is not this the carpenters son? Is not His mother called Mary, and His brothers, James and Joseph and Simon and Judas?”
Mark 6:2-3 - “And when the Sabbath had come, He began to teach in the synagogue; and the many listeners were astonished, saying, “Where did this man get these things, and what is this wisdom given to Him, and such miracles as these performed by His hands? “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?”
John 2:12 - “After this He went down to Capernaum, He and His mother, and His brothers, and His disciples; and there they stayed a few days.”
Acts 1:14 - “These all with one mind were continually devoting themselves to prayer, along with the women, and Mary the mother of Jesus, and with His brothers.”
1 Cor. 9:4-5 - “Do we not have a right to eat and drink? Do we not have a right to take along a believing wife, even as the rest of the apostles, and the brothers of the Lord, and Cephas?”
Gal. 1:19 - But I did not see any other of the apostles except James, the Lords brother.”
That Mary had other children is no less conjecture than that the brothers and sisters mentioned in Scripture were step brothers and sisters from Joesph's first marriage or that they were actually cousins.
Peace be with you.
Did you miss the posts about language?
The use of brothers is substituted for cousins.
Even Paul writes to the different areas/communities as “brothers.”