There is nothing in the NT to support your claim.
Mary, who was well aware of all of this history, nevertheless professes herself troubled and perplexed as to how this promised son could ever be engendered in her. Why would she not simply suppose that she'd get pregnant with her husband, just like the other holy mothers in Israel got pregnant with their husbands?
(2)Old Testament typology concerning the Ark of the Covenant and Mary (Theotokos). The Ark of the Covenant held the most sacred items of the Jewish faith: manna from the desert, the tablets of the 10 Commandment (the Law) and Aarons staff (Aaron was from the priestly tribe, so this was the staff of the priest, a shepherd for the people).
The Old Ark held the manna; Mary, the New Ark holds the Bread of Life. The Old Ark held the Law; Mary, the new Ark holds the Lawgiver and the very fulfillment of the Law. The Old Ark held the priestly staff; Mary, the New Ark holds the high priest, the Good Shepherd who pastors all souls.
No one was allowed to touch the Ark of the Covenant. The ark was pure (untouched). Mary the new Ark is pure, untouched. The Church teaches that she is ever-virgin, a vessel of purity.
(3) It's repugnant, and against the character of God, that He would initiate the Holy Incarnation of the Word by taking another man's wife --- if Mary were exclusively vowed to Joseph procreatively, as all other wives are to their husbands. If this were the way it happened, it would not a manifestation of God's infinite moral excellence. This would have been a defrauding of Joseph, a violation of the exclusivity of Mary and Joseph's marriage covenant: cuckoldry.
I'm saying God would not bump aside a natural husband who had an exclusive right to his wife's procreative future. Is this view in the NT?? Brother, this is the entire Bible: God's way is the honoring, not the violation, of holy covenants.
You can assert there's "nothing" to support the claim of Mary's pledged virginity --- her faithful and prior understanding that she belonged to God alone, God, the father of her Son --- only by failing to deeply consider the evidence.
Ignoring everything that supports the claim is not a persuasive strategy.