There is nothing said about intimate relations between Joseph and Mary after Jesus was born.
“knew her not” meant no intercourse had existed between them.
“not till she had brought her firstborn son and he called his name Jesus” meant she had no children previously and the first child was Jesus.
Anything after is pure speculation.
The Orthodox codified the terms ‘brother and sister’ to mean siblings and cousins in order to stop the speculation which existed in generations immediately following the crucifixion. It was important to early church leaders to keep the laity focused on the message of Christ and not the speculative fringes.
As Zefferelli had minor actors argue and scream during the film (my favorite) shooting of the trial of Jesus before the Sanhedrin “ I heard him say he would build the Temple in THREE days!” and another chiming in “No, I heard him say in TWO days!”. This is a sad part of human nature to zero in on trivia and not see the true important message.
Same with James as sibling brother of Jesus.
"And knew her not till she had brought forth her firstborn son: and he called his name JESUS" (AV).
"And he knew her not till she brought forth her first born son: and he called his name Jesus" (DRB).
The AV is translated from Greek as it is precisely given in Scrivener's Textus Receptus. Thayer's Greek-English lexicon, cited by e-Sword Bible software, limits the translational possibilities to:
G1097 (Strong's number)
γινώσκω
ginōskō
Thayer Definition:
1) to learn to know, come to know, get a knowledge of perceive, feel
1a) to become known
2) to know, understand, perceive, have knowledge of
2a) to understand
2b) to know
3) Jewish idiom for sexual intercourse between a man and a woman
4) to become acquainted with, to know
Part of Speech: verb
A Related Word by Thayer’s/Strong’s Number: a prolonged form of a primary verb
Citing in TDNT: 1:689, 119
(Actually, my 1889 edition of Thayers gives 15 column inches to γινώσκω, and anothe 4 inches to synonyms. TDNT ia abbreviation for Theological Dictionary of the New Testament, another 10-volume work.) However the above is quite adequate to describe the use of γινώσκω in this context; and in Thayers the only use of Mt. 1:25 is as follows:
γινώσκω
Case I.3. by a Hebraistic euphemism [cf. W. 18], found also in Grk. writ. fr. the Alexandrian age down, γινώσκω is used of the carnal connection of male and female, rem cum aliquo or aliqua habere(cf. our have a [criminal] intimacy with): of a husband, Mt. i.25; of the woman Lk. i.34; (Gen. iv.1,17;xix:8; 1 Sam. i.19, etc.; Judith xvi.22; . . . (other citations from Classical Greek ).
This use of γινώσκω is very particular and peculiar in that it does refer only to the expected connubial joining of a lawfully joined husband and wife. Because of the particular relationship of espousal, then cohabitation, Thayer's definitions af 1, 2, and 4 above can not possibly apply either preceding or going on from the birth of Jesus. Thus only Definition 3 above can possibly apply. Mary herself used the term herself in Luke, speaking to Gabriel, as to being "known."
What we have here is that, up until her first birth, Joseph did not know her (nor indeed not before her puriication subsequent to her first birthing experience). In comparison with the verb "to know by experience" which is not used for describing husband/wife relations in the lexicons:
επιγινώσκω is inclined toward knowledge of intellectual or spiritual things by personal experience and familiarity, and is not used of the carnal knowledge of a woman.
The second Greek word of concern here is εως, translated as "till." Strong's lexicon gives an accurate description of the use of this word in this sentence:
G2193
εως
heōs
heh'-oce
Of uncertain affinity; a conjugation, 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).
Thus this word--which means "until"--introduces the inescapable prescience of the nature of marital conduct of Joseph and Mary subsequent to the birth of (not Joseph's) child. Clearly, the Holy Ghost offers this very clear, unambiguous sense of their ongoing life as husband and wife.
As an aside, I know that as an only child for many years, you cannot learn by experience what it is like to be raised with conjoint siblings. There is absolutely no reason, other than to prop up the "Immaculate Conception" doctrine, that Jesus should not have had the knowlrdge by experience of being raised in a family with siblings to relate to.
Thirdly, if Mary was never to have another child, for what reason would the Holy Ghost insist on inscripturating the term "first born" here, rather than "only" if that were the precise thought (which it is not)? As God's Son, Hei is called by God "My Only Begotten . . ." (in the flesh, not of The Spirit) ". . . Son" as in Jn. 3:16. God never proclaimed Mary as His begotten-in-the-flesh daughter, did he?
Mary had other children, begotten of her righteous, faithful, law-abiding, Spirit-controlled husband Joseph to consummate the tasks as a Christian wife to a godly husband who certainly desired to raise more godly generations, and proceeded to do so.
The DRB, translated from the Latin of Jerome, who translated much of the Vulgate from the early Koine texts, explicitly says the same things.
The rule of interpretation is that when the plain sense of the Scripture make common sense, to seek no other sense.
Declaring Mary as being more holy by renouncing marriage vows is simple foolishness, and contradicts both the particular context, as well as the other, broader Scriptural setting that declares that Jesus had siblings that rejected his calling, for a time, with whom his mother sided, also in that time.
Anything after is pure speculation.
Anything that rejects the simple, plain, commonsense understanding of what the Holy Ghost has placed in Scripture regarding this is not only arbitrary conjecture, it is wild-eyed madness when dogma laid down regarding Mary's everlasting virginity is forced on a credulous, unbelieving follower who is turned away from the Jesus of the Bible, to another Jesus--of the same kind, but yet another--with another gospel and another spirit, both of a different kind, that blocks the seeker from knowing what he/she needs to trust in to be saved. IMHO