"(W)as/is a perpetual virgin?" You got me on that one. Sorta like being a little bit pregnant.
The Holy Scriptures refer to brothers and sisters of the Lord, but the Church (both in the East and West) has always taught that they were family relations of the Lord, i.e. cousins or "step" brothers and sisters. The word translated has this broad meaning, in Hebrew, Aramaic, and Greek. There have been several Posts/Articles on FR concerning this topic, and I off hand don't know where to direct you. Maybe somebody a little more up on where to go, can.
In any event, I thought it would be fun to mention a treatise that St. Jerome wrote in the 4th Century concerning this very topic. I had always remembered the treatise as being very good and "current". I checked the internet and voila! Here it is:
Not too long, and it covers Catholic thought and teaching on this subject very well from one of the great Fathers of the Church. He says it better than I ever could.
This has been the teaching of the Orthodox Church on this matter from the earliest centuries. The family history, though not the childhood narratives concering Christ, in the Proto-Evangelion of James are sound. St. James is titled Brother of the Lord by the Orthodox because alone of Jesus' stepbrothers he was willing to share his inheritance with him.
Christ's entrusting of Mary to St. John at the time of His Crucifixion is testimony both that the aged Joseph had died during the time of Our Lord's earthly ministry and that she had no other children, as Jewish law and custom would have entrusted her to their care.