Oh my! I am surprised at your RCIA leaders. They should know better. Mary’s perpetual virginity is one of our most fundamental truths!
As for your other question. I do know that one of the Gospels (sorry, I don’t have the exact reference here) mentions Jesus’ “mother and brothers” being present. Many people automatically jump to the conclusion that He therefore had siblings, but actually the Church teaches that He was Mary’s only child. I believe the Church recognizes that that particular passage was written in the language of that time; although it said “brothers” they were probably some relatives of His, cousins or such. Hope that helps!