Of course one can go right to the source, Saint Iakovos (James) the son of Saint Joseph the Betrothed from his first marriage, who wrote a document in the early 100's explaining the lie of his step-mother, Mary, the Theotokos. It wasn't included in the Bible, because it was not telling us how to work out our salvation, as the rest of the New Testament does. But you can read it here on this blog: The Protoevangelium of James.
Martin Luther (Founder of the 1520 A.D. Lutheran Religion) believed that Mary did not have other children and did not have any marital relations with Joseph. The Latin text of the 1537 Smalcald Articles, written by Martin Luther, used the term "Ever Virgin" to refer to Mary. The perpetual virginity of Mary was Luther's lifelong belief, even after he rejected other Marian doctrines.
Huldrych Zwingli (A Founder of the 1522 A.D. Reformed Protestant Religion) directly supported perpetual virginity and wrote: "I firmly believe that the Theotokos, ... forever remained a pure, intact Virgin." Like Zwingli, the English reformers also supported the concept of perpetual virginity. Luther and Zwingli's support of perpetual virginity was endorsed by Heinrich Bullinger and was included in the 1566 Second Helvetic Confession.
John Calvin (Founder of the 1530 A.D. Calvinist Religion) cautioned against "impious speculation" on the topic.
King Henry VII of England (Founder of the 1534 A.D. Anglican and Episcopal Religions) supported perpetual virginity "on the basis of ancient Christian authority".
John Wesley (Founder of the 1739 A.D. Methodist Religion) one of the founders of Methodism, also supported the doctrine and wrote that: "... born of the blessed Virgin Mary, who, as well after as before she brought Him forth, continued a pure and unspotted virgin.
A passage all the Protestant Founders used to support the doctrine of perpetual virginity is of the sayings of Jesus on the cross, i.e. the pair of commands first to his mother "Woman, behold your son!" and then to his disciple "Behold, thy mother!" in The Gospel According to Saint John 19:26-27. The Gospel then states that "from that hour the disciple took her unto his own home". Since the time of the Church Fathers this statement has been used to reason that after the death of Jesus there was no one else in the immediate family to look after Mary, and she had to be entrusted to the disciple given that she had no other children.