[kosta50]

Matthew 1:25 And knew her not till she had brought forth her firstborn son: and he called his name JESUS

That simply means, in the past tense, that she was a virgin -- that up to that time there was no conjugal relationship between +Joseph and Mary.

The verse does not say "he knew her after she had brought forth her firstborn..." so, ad minimum, the Protestants should remain neutral, because the Bible is silent on what transpired afterwords.

[Full Court]

1 Kings 1:4
And the damsel was very fair, and cherished the king, and ministered to him:
but the king knew her not.

Matthew 1:25
And knew her not till
she had brought forth her firstborn son: and he called his name JESUS.