[annalex]

when one looks at the actual greek, there is not a question that Joseph knew Mary. Rather, the Bible states that he witheld from marital relations with her UNTIL (or up to the time when) Jesus was born. Mat 1:25

There is no indication what happened after Christ was born in Matthew 1:25 because "eos" can just as easily mean "evel till". Compare Mt. 27:8, "the field was called Haceldama, that is, The field of blood, [eos] this day.".

"Firstborn" is legal status that has nothing to do with subsequent children or their gender.

[Blogger]

It's not the same. The rule is when it is found with ou or outou it means until the time when. See again Thayer's Lexicon http://www.blueletterbible.org/cgi-bin/words.pl?book=Mat&chapter=27&verse=8&strongs=2193&page=1&flag_full=1

This rule for use of EWS does not apply in Matthew 27:8