You believe what someone told you God's word said.<quoted text>
You follow the teaching of mere natural men.
A. They teach you Mary remained a virgin evermore. God's Word says Joseph took her to wife...you choose to believe men instead of God....I believe God.....
'Mary's question (Luke 1:34), the angel's answer (Luke 1:35-37), Joseph's way of behaving in his doubt (Matthew 1:19-25), Christ's words addressed to the Jews (John 8:19) show that Mary retained her virginity during the conception of her Divine Son.
As to Mary's virginity after her childbirth, it is not denied by St. Matthew's expressions "before they came together" (1:18), "her firstborn son" (1:25), nor by the fact that the New Testament books repeatedly refer to the "brothers of Jesus". The words "before they came together" mean probably, "before they lived in the same house", referring to the time when they were merely betrothed; but even if the words be understood of marital intercourse, they only state that the Incarnation took place before any such intercourse had intervened, without implying that it did occur after the Incarnation of the Son of God.
 Matt., xii, 46-47; xiii, 55-56; Mark, iii, 31-32; iii, 3; Luke, viii, 19-20; John, ii, 12; vii, 3, 5, 10; Acts, i, 14; I Cor., ix, 5; Galatians 1:19; Jude, 1
 cf. St. Jerome, in Matt., i, 2 (P.L., XXVI, 24-25)'
Source link: http://www.newadvent.org/cathen/15464b.htm