“Sure I can, because it is a knowledge possessed by the Church, which is not expressed in the scripture.”
Where did this “knowledge” come from? I ask. And When?
Ther historical knowledge of the Church regarding Mary started with the Apostles and the Evangleists. Scripture tells us that Mary lived with St. John the Evangelist. St. Luke somehow gained knowledge of her youth, one that had no public witness, including the ability to cite verbatim her Magnificat prayer (Luke 1:46-55). This indicates the St. Luke received that knowledge, most likely, from Mary directly, or perhaps from someone closely associated with her.