UndercoverMan said^ But doesn't the Orthodox Church recognize Mary under the title Theotokos which translates as "God-bearer", "Birth-Giver of God" or "the one who gives birth to God"?
Catholics and most mainline Protestant churches also believe in the Trinity.
Virgin Mary is the Theotokos. When Mary is mentioned in our Orthodox services, we use the title "all-holy, immaculate, most blessed and glorified lady, the Theotokos and ever-virgin Mary".
There are things in the NT which seem to indicate that Mary did not remain a virgin AFTER the birth of Jesus. In any case, there is nothing that I have seen in the NT to indicate that she did remain a virgin after the birth of Jesus. It is unclear why many people insist that she did remain a virgin.
Virginity of Mary is part of the Early Holy tradition. Different Christian denomination hold different accounts of her life, however, most early ones (preserved in the apocrifical texts) suggest that Joseph was an old man and keeper of Mary. I.e. the intent for him was not to be Mary's husband per se, but rather her keeper. In the Gospel there is a passage that he "did not know her" until she gave birth to her first born. Same time such does not imply that marriage was physically consummated thereafter. If to explore the NT we will not find much evidence to Mary' ever virginity, however, as the Church interprets Daniel 2:34-35. In Greek and Slavonic translations the rendition, emphasis is not only on the rock that fall of the mountain as not cut by human hands, but to the very mountain that was not touch by human hands. Again, most of it is via exegesis and corresponding tradition, not direct NT narrative.
Here are some links I found.
Any mention of brothers or sisters of Jesus can be explained as cousins or children of Joseph's but not with Mary. Something telling in the scriptures that tells me that Jesus had no brothers and sisters through Mary was that Mary was alone at the crucifixion. There is no mention of any other of her children with her when their brother is being executed. It would stand to reason anyone of us would be with our Mother during such an ordeal. Another telling thing is that Jesus from the cross tasks the apostle John with looking after His Mother. If Mary had any other biological children this would have been unnecessary.
25 Now there stood by the cross of Jesus His mother, and His mother’s sister, Mary the wife of Clopas, and Mary Magdalene. 26 When Jesus therefore saw His mother, and the disciple whom He loved standing by, He said to His mother, “Woman, behold your son!” 27 Then He said to the disciple, “Behold your mother!” And from that hour that disciple took her to his own home.