That Mary remained virgin all her life is a historical fallacy made up by the Church.
It can NEVER be proved. Only presumed.
There are things that I know about my parents and grandparents that are a fact but I cannot prove it to you. I bet, you, too, know something about your family that cannot be proven to outsiders. You just know it. This is what Christian faith is: belief in the factual nature of the events teh memory of which was retained by the Chruch since these events happen.
But Protestants killed their own faith. They want to turn the Church that nse was theit home into a police station with evidence filed away. That is the chief damage that Sola Scriptura does to a Christian soul.