Mary wasn't a virgin when she died!
Matthew wouldn't have wrote the following if Mary didn't have more children afterwards. If was written in a past tense.
Matthew 1:25
25.
|2532| and
|3756| not
|1097| did have sexual relations with
|0846| her
|2193| until
|9999| {after}
|3739| -
|5088| she gave birth to
|3588| the
|5207| son
|0846| of her,
|3588| the
|4416| firstborn.
|2532| And
|2564| he called
|3588| the
|3686| name
|0846| of him,
|2424| JESUS.
Strong's Number: 2193
Transliterated: heos
Phonetic: heh'-oce
Text: of uncertain affinity; a conjunction, preposition and adverb of continuance, until (of time and place): --even (until, unto), (as) far (as), how long, (un-)til(-l), (hither-, un-, up) to, while(-s).
Strong's Number: 3739
Transliterated: hos
Phonetic: hos
Text: including feminine he {hay}; and neuter ho {ho}; probably a primary word (or perhaps a form of the article 3588); the relatively (sometimes demonstrative) pronoun, who, which, what, that: --one, (an-, the) other, some, that, what, which, who(-m, -se), etc. See also 3757.
http://www.blueletterbible.org/faq/nbi/199.html
http://www.jesus-is-lord.com/virgin.htm