Marian teaching simply ignores what is really in the Bible and the story is more dramatic with Thomas/Jude as Jesus brother, Simon the Zealot as well.  It tells you Mary was a bit more radicalized than the champion of chastity the Church wants to maker.  I have no quarrel with Assumption and Immaculate Conception as narrative, although the latter is not necessary if original sin is the human tendency to blame rather than some sexually transmitted stain of disobedience by two people who never existed.  Would a Mary who had sex ruin your respect for her?  It would not bother me.  Your parents had sex too, by the way.