Dr. Muhammad Abu Laylah, professor of the Islamic Studies & Comparative Religions at Al-Azhar Univ. states: Marry, according to Islam, did not marry at all whether before giving birth to Jesus or after that. She was chosen by Allah and prepared for this specific task, i.e. giving birth to Jesus (peace and blessings be upon him). Almighty Allah says, “And when the angels said: O Mary! Lo! Allah hath chosen thee and made thee pure, and hath preferred thee above (all) the women of creation. O Mary! Be obedient to thy Lord, prostrate thyself and bow with those who bow (in worship). This is of the tidings of things hidden. We reveal it unto thee (Mohammad). Thou wast not present with them when they threw their pens (to know) which of them should be the guardian of Mary, nor wast thou present with them when they quarrelled (thereupon). (And remember) when the angels said: O Mary! Allah giveth thee glad tidings of a word from Him, whose name is the Messiah, Jesus, son of Mary, illustrious in the world and the Hereafter, and one of those brought near (unto Allah). He will speak unto mankind in his cradle and in his manhood, and he is of the righteous. She said: My Lord! How can I have a child when no mortal hath touched me? He said: So (it will be). Allah createth what He will. if He decreeth a thing, He saith unto it only: Be! and it is. And He will teach him the Scripture and wisdom, and the Torah and the Gospel. And will make him a messenger unto the children of Israel, (saying): Lo! I come unto you with a sign from your Lord. Lo! I fashion for you out of clay the likeness of a bird, and I breathe into it and it is a bird, by Allah’s leave. I heal him who was born blind, and the leper, and I raise the dead, by Allah’s leave. And I announce unto you what ye eat and what ye store up in your houses. Lo! herein verily is a portent for you, if ye are believers. And (I come) confirming that which was before me of the Torah, and to make lawful some of that which was forbidden unto you. I come unto you with a sign from your Lord, so keep your duty to Allah and obey me. Lo! Allah is my Lord and your Lord, so worship Him. That is a straight path.” (Aal `Imran 3: 42-50)

Of course, in the Gospels she was betrothed to Joseph the Carpenter and later after Jesus she has some siblings to Jesus. In Islam, nothing like that is proven.”