There is already another thread about this in the main apologetics forum, but your question hasn’t been addressed there.
To help answer your question – Mary was actually betrothed before the appearance of the angel. So, the real question is – why would Mary have become betrothed to a man if she had taken a vow of celibacy? The angel telling Joseph to do so is simply not valid, as they were betrothed before that.
If you do some proper research for a change, you will discover that celibate marriages were contracted among Jewish couples. The Jewish catacombs in Rome contain the names of some of these rare couples. Joseph was chosen by God to be the wife of Mary and the foster father of Jesus, for he too was a chaste man. Meanwhile, Matthew does not explicitly say that Mary and Joseph had no relations until “after” the birth of Jesus. He is referring to the time of their betrothal and marriage before the birth of Christ to stress the truth of the virgin birth and the fullfillment of Isaiah’s prophecy.
“I tell you, among those born of women there has risen no one greater than John the Baptist; yet he who is least in the kingdom of heaven is greater than he.” ( Matthew 11:11; cf. Luke 7:28)
According to Sacred Tradition, Mary is perfect in every way, including her perfect virginity, because of her Immaculate Conception. Both Jesus and Mary are greater than John.
“For the Mighty One has done great things for me, and holy is his name.”
{ Luke 1:49}
“The Son of God…was born perfectly of the holy ever-virgin Mary by the Holy Spirit.”
Epiphanius, ‘Well Anchored Man’, 120 (A.D. 374)
“The friends of Christ do not tolerate hearing that the Mother of God ever ceased to be a virgin.”
Basil, ‘Homily In Sanctum Christi generationem’, 5 (A.D. 379)
“If anyone does not confess that the holy and ever-Virgin and immaculate Mary did not conceive without seed by the power of the Holy Spirit the very Word of God, give birth to him without corruption, thereafter that very virginity remaining ever integral, let him be anathema.”
Pope Martin 1, Lateran Synod in Rome (A.D. 649)
Pax vobiscum
Good Fella
