www.bible.ca (I only use this because it follows scripture and it takes less time for me to make the point)
Concerning Mary being a Virgin after giving birth to Jesus and not having sons and daughters later; we all have to remember that she was a “vessel”, a “human being”, blessed, yes, but still flesh and blood. She did not even understand what was happening totally because if she did, then she would have been His equal, such as your question suggested, “co-redeemers”. Jesus was flesh and blood but God in the flesh. She was not a “goddess”.
"Matthew 13:55-56 & Mark 6:3
Cannot simply be cousins because Colossians 4:10 uses a separate Greek word. John 1:41 uses the same term of Peter and his brother.
The Catholic Catechism says of these verses: “The Church has always understood these passages as not referring to other children of the Virgin Mary. In fact James and Joseph, ‘brothers of Jesus,’ are the sons of another Mary, a disciple of Christ…” Pg. 126 #500).
The Catholic church teaches that the Mary in these passages is the mother of Jesus, but Jesus brothers and sisters are children of another woman also named Mary. The children are so clearly the offspring of the “Mary” of this passage, that the Pope has come to the conclusion is must be a different Mary! Incredible!
Now read it for yourself from the scripture and see if you agree with the Catholic church that the Mary of these passages is both the mother of Jesus and the mother of James and Joseph and Simon and Judas.
Matthew 13:55-56 "Is not this the carpenter’s son? Is not His mother called Mary, and His brothers, James and Joseph and Simon and Judas? 56 “And His sisters, are they not all with us? Where then did this man get all these things?” 57 And they took offense at Him. But Jesus said to them, “A prophet is not without honor except in his home town, and in his own household.”
Mark 6:3 “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?” And they took offense at Him. 4 And Jesus said to them, “A prophet is not without honor except in his home town and among his own relatives and in his own household.”
Oh, did I mention, I took 3 religion courses and a philosophy course at a catholic university? So you see, I do have some knowledge about some of this information besides just this website. I still made “A’s” in the courses

The instructor was a minister. He almost wanted me to teach the course. I believe “The Synoptic Gospels” was one of the books we used. Very interesting read into borrowing scriptures from this or that to make another book or 2 or 3.