Mary's perpetual virginity has zero effect on Jesus' ability to redeem us from sin on the cross. Catholics consider marriage a sacrament, yet one Catholic on here told me years ago that Mary was a sacred vessel that God used to bring His Son into the world and as such, she had to remain so, and not be given back to Joseph for "common use." So, since when is marriage, a sacrament in the RCC, "common usage" between a husband and wife? If it is a holy sacrament?
Nowhere does the Bible refer to Mary as the new Eve or ark of the New Covenant. Nowhere. Not even a hint. But even if it did teach such things, that still would not preclude Mary and Joseph having children together in the bonds of holy and lawful matrimony, which is blessed by God since Adam and Eve.
There is no reason in the world that, after Jesus was born, and her period of purification was finished, Mary and Joseph could not have resumed a normal, married life, and joyfully raised up more children together, children of Joseph's body. I think God graciously gave them back to each other, blessing both of them with more children for their humble obedience.