A Roman Catholic "study Bible" says this:
The Greek heōs does not imply that Joseph and Mary had marital relations following Jesus' birth. This conjuction is often used (translated "to" or "till") to indicate a select period of time, without implying change in the future (2 Sam. 6:23 [LXX]; Jn 9:18; 1 Tim 4:13). Here Matthew emphasizes only that Joseph had no involvement in Mary's pregnancy before Jesus' birth. Mary's perpetual virginity is firmly established in Church tradition. Its doctrinal formulation is traced to the Lateran Synod of A.D. 649 and was reaffirmed in 1968 by Pope Paul VI.
An Eastern Orthodox "study Bible" says this:
The use of the word till does not imply that Joseph had marital relations with Mary after the Savior's birth. In the Bible, this word (sometimes translated as "to") is often used to express a situation that actually continues after the event mentioned (see 28:20; Gn. 8:7; Dt. 34:6; 2Kg 6:23). The witness of the entire Church throughout history is that Mary remained a virgin for life.
Yes. Mary's perpetual virginity is established in church tradition—not in Scripture and certainly not in fact. Church history certainly does not witness to Mary remaining a virgin for life. Show me the writings of any of the Apostles who taught or believed such a thing. Show me the writings of any disciple of any of the Apostles who taught or believed such a thing. Polycarp? Irenaeus?
What does history actually look like?
It was not until the apocryphal work Protogospel of James (c. 150) that the perpetual virginity of Mary was ever mentioned or postulated. Tertullian (160-220) denied the virginity of Mary after Jesus' birth. Origen (184-253), however, taught it. In the East, Athanasius (296-373) defended it vehemently. Basil the Great (330-379) accepted it, but did not consider it to be a dogma. In the West, Jovinian (?-405) and Helvidius (340-390) denied the perpetual virginity while Ambrose (340-397), Jerome (347-420), and Augustine (354-430) staunchly defended it. As the church became more perverse in its beliefs and practices, and eventually evolved into the Catholic church, the Lateran Synod is when this tradition became entrenched, later to be clutched to by both the Roman Catholic church and the Eastern Orthodox church from the Great Schism of 1054 onward.
The early witness of the early church does not support the perpetual virginity of Mary. Certain Christians began to accept it, from whatever sources of influence, while others rejected it based on the testimony of the Scriptures in Greek. The first appearance of this concept was in an uninspired apocryphal work. Jerome seems to have been the biggest defendant of this error, having condemned Jovinian as a "heretic" not only for speaking against the perpetual virginity of Mary, but also for having praised the excellence of marriage. It was Jerome himself who was the heretic, as Jovinian's argument for marriage was based entirely, and solidly, upon the Scriptures.
"I do you no wrong, Virgin: you have chosen a life of chastity on account of the present distress: you determined on the course in order to be holy in body and spirit: be not proud: you and your married sisters are members of the same Church… Now concerning virgins I have no commandment of the Lord: but I give my judgement, as one that hath obtained mercy of the Lord to be faithful. I think therefore that this is good by reason of the present distress, namely, that it is good for a man to be as he is… See, the Apostle confesses that as regards virgins he has no commandment of the Lord, and he who had with authority laid down the law respecting husbands and wives, does not dare to command what the Lord has not enjoined. And rightly too. For what is enjoined is commanded, what is commanded must be done, and that which must be done implies punishment if it be not done. For it is useless to order a thing to be done and yet leave the individual free to do it or not do it. If the Lord had commanded virginity He would have seemed to condemn marriage, and to do away with the seed-plot of mankind, of which virginity itself is a growth. If He had cut off the root, how was He to expect fruit ? If the foundations were not first laid, how was He to build the edifice, and put on the roof to cover all ! Excavators toil hard to remove mountains; the bowels of the earth are pierced in the search for gold. And, when the tiny particles, first by the blast of the furnace, then by the hand of the cunning workman have been fashioned into an ornament, men do not call him blessed who has separated the gold from the dross but him who wears the beautiful gold. Do not marvel then if, placed as we are, amid temptations of the flesh and incentives to vice, the angelic life be not exacted of us, but merely recommended. If advice be given, a man is free to proffer obedience; if there be a command, he is a servant bound to compliance."
Jerome, in his blatant ignorance, took an entire book to praise virginity and disparage the state of marriage; that holy state which God in His Holy Word says should be "held in honor among all" (Heb. 13:4). That holy union that is a picture of Christ and His bride, the Church. Why would Jerome disparage something that is a picture of Christ and His Church? Sheer ignorance based on his sources of influence.
According to Scripture, Mary clearly had other children, which strongly implies that she and Joseph had normal marital relations after Jesus. In Mark, a crowd asks of Jesus, “Is not this the carpenter, the son of Mary, and brother (adelphos, ἀδελφὸς) of James and Joses and Judas and Simon? Are not His sisters here with us?” (6:3). In Luke, when Jesus is told by a crowd gathered to hear him speak, “Your mother and Your brothers (adelphos, ἀδελφὸς) are standing outside, wishing to see You,” Jesus famously answers them: “My mother and My brothers (adelphos, ἀδελφὸς) are those who hear the word of God and do it” (8:19-21). John writes that after Jesus had performed His first miracle in Cana, “He went down to Capernaum, He and His mother and His brothers (adelphos, ἀδελφὸς) and His disciples; and they stayed there a few days” (2:12).
The Roman Catholic and Eastern Orthodox churches attempt to argue that adelphos (ἀδελφὸς) does not merely mean "brothers," but that it can also mean "step-brothers" or "cousins." This was Jerome's argument, but this assertion is false. Regarding Peter and Andrew, they were adelphos (ἀδελφὸς)—brothers. Regarding John and James, they were adelphos (ἀδελφὸς)—brothers. Mary and Martha were adelphe (ἀδελφή)—sisters. The word adelphos (ἀδελφὸς) means "brothers," whether literally or figuratively. The figurative sense is used repeatedly throughout the New Testament in regard to our "brothers" (adelphos, ἀδελφὸς) in the church; our "brothers" (adelphos, ἀδελφὸς) in Christ. The word for "cousin" (relative, kin) is suggenes (συγγενής), which is what Elizabeth was to Mary.
Jerome argued that these "brothers" were either step-brothers, older sons of Joseph from a previous marriage (of which nothing is mentioned in Scripture), or merely cousins. Throughout the entire birth narrative and childhood narrative, there is never any mention of any other children. So where were these older step-brothers during all of this? The argument for them being step-brothers attempts to use two verses for its support. The first verse: In the upper room were "Mary the mother of Jesus, and . . . His brothers" (Acts 1:14). The argument is that it does not say "her sons," but rather "His brothers." The reason it says "His brothers" is because Jesus is the focus here—not Mary. Jesus is the object. The second verse: On the cross, Jesus looks to John, His disciple, and says, "Behold, your mother!" The argument is that He did not say this to any of His family, but to a complete stranger, implying that she must have been alone. Jesus did not give this responsibility to his brothers because they were not sympathetic to His ministry, nor did they believe in Him, and they likely were not present at the time.
Let us assume these "brothers" were indeed older step-brothers. Even if this were the case, Mary still was not a perpetual virgin. "[Joseph] did not have sexual relations with [Mary] until she gave birth to a Son; and he called His name Jesus" (Matt. 1:25). Even if you attempt to argue for the word "to" to be translated instead of "until," the word is pointing toward a specific point—the "birth of a Son." Heōs (ἕως) is a conjunction, preposition, and adverb of continuance. The word signifies something that "continues up to a certain time." She remained a virgin "until the time when" she gave birth. After the birth of Christ, she was no longer a virgin because she and Joseph engaged in normal marital relations. To argue that they did not is to create a huge problem, which Paul addressed in 1 Corinthians 7:3-5. If Joseph never touched Mary, he would have burned with desire and taken that desire elsewhere, which would have made him an adulterer. The doctrine of the perpetual virginity of Mary has many holes and creates many problems within the rest of Scripture.
The Greek does not support the perpetual virginity of Mary. The writings of the Apostles do not support the perpetual virginity of Mary. The writings of the earliest disciples of the Apostles do not support the perpetual virginity of Mary. The perpetual virginity of Mary is entrenched solely in the traditions and errors of the Roman Catholic and Eastern Orthodox churches. Scripture repudiates these very teachings. Anathema upon any heretic who teaches and proclaims this false doctrine!