What is the support or arguments to indicate the age of the Virgin Mary at Jesus’ birth?
It is slim pickings to find any support or arguments to indicate the age of Mary at the birth of Jesus. But slim, does not mean there are none.
According to the apocryphal Gospel of James, Mary was the daughter of Saint Joachim and Saint Anne. Before Mary's conception, Anne had been barren and was far advanced in years. Mary was given to service as a consecrated virgin in the Temple in Jerusalem when she was three years old, much like Hannah took Samuel to the Tabernacle as recorded in the Old Testament.
Pertinent quote (emphasis added):
And when she was twelve years old there was held a council of the priests, saying: Behold, Mary has reached the age of twelve years in the temple of the Lord. What then shall we do with her, test perchance she defile the sanctuary of the Lord? And they said to the high priest: Thou standest by the altar of the Lord; go in, and pray concerning her; and whatever the Lord shall manifest unto thee, that also will we do. And the high priest went in, taking the robe with the twelve bells into the holy of holies; and he prayed concerning her. And behold an angel of the Lord stood by him, saying unto him: Zacharias, Zacharias, go out and assemble the widowers of the people, and let them bring each his rod; and to whomsoever the Lord shall show a sign, his wife shall she be. And the heralds went out through all the circuit of Judaea, and the trumpet of the Lord sounded, and all ran.
- And Joseph, throwing away his axe, went out to meet them; and when they had assembled, they went away to the high priest, taking with them their rods. And he, taking the rods of all of them, entered into the temple, and prayed; and having ended his prayer, he took the rods and came out, and gave them to them: but there was no sign in them, and Joseph took his rod last; and, behold, a dove came out of the rod, and flew upon Joseph's head. And the priest said to Joseph, Thou hast been chosen by lot to take into thy keeping the virgin of the Lord. But Joseph refused, saying: I have children, and I am an old man, and she is a young girl.
Some apocryphal accounts state that at the time of her betrothal to Joseph, Mary was 12–14 years old. According to ancient Jewish custom, Mary could have been betrothed at about 12. Hyppolitus of Thebes says that Mary lived for 11 years after the death of her son Jesus, dying in 41 AD.
The earliest extant biographical writing on Mary is Life of the Virgin attributed to the 7th-century saint, Maximus the Confessor, which portrays her as a key element of the early Christian Church after the death of Jesus.
In the 19th century, a house near Ephesus in Turkey was found, based on the visions of Anne Catherine Emmerich, an Augustinian nun in Germany. It has since been visited as the House of the Virgin Mary by Roman Catholic pilgrims who consider it the place where Mary lived until her assumption. The Gospel of John states that Mary went to live with the Disciple whom Jesus loved,[Jn 19:27] identified as John the Evangelist.[Jn 21:20-24] Irenaeus and Eusebius of Caesarea wrote in their histories that John later went to Ephesus, which may provide the basis for the early belief that Mary also lived in Ephesus with John. - Mary, mother of Jesus
The Catholic Encyclopedia has the following to say on this subject:
It is probably at Nazareth that Joseph betrothed and married her who was to become the Mother of God. When the marriage took place, whether before or after the Incarnation, is no easy matter to settle, and on this point the masters of exegesis have at all times been at variance. Most modern commentators, following the footsteps of St. Thomas, understand that, at the epoch of the Annunciation, the Blessed Virgin was only affianced to Joseph; as St. Thomas notices, this interpretation suits better all the evangelical data.
It will not be without interest to recall here, unreliable though they are, the lengthy stories concerning St. Joseph's marriage contained in the apocryphal writings. When forty years of age, Joseph married a woman called Melcha or Escha by some, Salome by others; they lived forty-nine years together and had six children, two daughters and four sons, the youngest of whom was James (the Less, "the Lord's brother"). A year after his wife's death, as the priests announced through Judea that they wished to find in the tribe of Juda a respectable man to espouse Mary, then twelve to fourteen years of age. Joseph, who was at the time ninety years old, went up to Jerusalem among the candidates; a miracle manifested the choice God had made of Joseph, and two years later the Annunciation took place. These dreams, as St. Jerome styles them, from which many a Christian artist has drawn his inspiration (see, for instance, Raphael's "Espousals of the Virgin"), are void of authority; they nevertheless acquired in the course of ages some popularity; in them some ecclesiastical writers sought the answer to the well-known difficulty arising from the mention in the Gospel of "the Lord's brothers"; from them also popular credulity has, contrary to all probability, as well as to the tradition witnessed by old works of art, retained the belief that St. Joseph was an old man at the time of marriage with the Mother of God. -
Her betrothal to Joseph
The apocryphal writings to which we referred in the last paragraph state that Mary remained in the Temple after her presentation in order to be educated with other Jewish children. There she enjoyed ecstatic visions and daily visits of the holy angels.
When she was fourteen, the high priest wished to send her home for marriage. Mary reminded him of her vow of virginity, and in his embarrassment the high priest consulted the Lord. Then he called all the young men of the family of David, and promised Mary in marriage to him whose rod should sprout and become the resting place of the Holy Ghost in form of a dove. It was Joseph who was privileged in this extraordinary way.
Although we may never know for sure how old Mary was at that time, there are a few hints of possibility here and there.
We have already seen that St. Gregory of Nyssa, St. Germanus of Constantinople, and pseudo-Gregory Nazianzen seem to adopt these legends. Besides, the emperor Justinian allowed a basilica to be built on the platform of the former Temple in memory of Our Lady's stay in the sanctuary; the church was called the New St. Mary's so as to distinguish it from the Church of the Nativity. It seems to be the modern mosque el-Aksa. - The Blessed Virgin Mary
Most scholars accept that marriage of first century maidens in Palestine was possible after the age of twelve (12).
Jewish betrothal is not like the Gentile concept of engagement, which is only a promise of marriage. The betrothal stage was also called kiddushin, "sanctification," and meant that from that point the woman belonged to the man. The word kiddushin comes from the same root word as kadosh ("holy"). Just as kodesh (holy things) are forbidden to all but those for whom they are designated, so too does this woman become forbidden to all men but to whom she has now been designated. Betrothal made the woman a legal wife and her status could only be changed by divorce or death. Betrothal was usually accomplished by the groom giving a coin or ring to the prospective bride and her acceptance of the token accomplished kiddushin.
Scripture provides no information on the typical age for formal betrothal. The classification of "virgin" does not denote age. A girl did become accountable to the Torah (Heb. bat mitzvah, "daughter of the commandment") and thus treated as an adult when she became twelve years and a day old (B.K. 87b; Ket. 39a; Kidd. 63b; Nidd. 5:6; Yom. 8:3). Adulthood for a girl was not only determined by age but also by her having passed through puberty, that is possessing breasts and pubic hair (Kidd. 81b; Ezek 16:7-8; cf. SS 8:8). Once a girl had passed through puberty she would be eligible for marriage (Nidd. 45a). Since marriages were often arranged by parents a girl could be selected for her future husband before bat mitzvah. Talmudic literature does speak of the typical age of marriage for males as 18 (Avot 5:21), but marriage might also take place anywhere from 16-24 years of age (Kidd. 29b-30a). - Marriage in Ancient Israel
Further information may be gleaned from the following articles: