Very few first-century Jews were Nazirites (there is no Scriptural evidence that Joseph was one), and anyway, Nazirite vows have never been deemed to include celibacy.
You can't know that there were very few first-century Jews who were Nazirites, especially when Jewish people are heavily into traditions. It's possible that Joseph was a Nazirite, and if he was, whether or not you believe that Nazirite vows included celibacy, at the very least it meant he would've been someone accustomed to taking vows of dedication for God in general, and thus more understanding of Her vow, and willing to join Her in it.
And I stand by my comment that "No first century Jewish man would be likely to marry a professed perpetual virign." Is it possible that one would? Sure. Is it likely? No.
God ab aeterno would've
thought of Mary and Her role in the redemption of mankind, and thus Mary and everything surrounding Her has never and will never be a "normal" situation, because She, a human, was chosen to be the
Mother of God Incarnate and the Messiah. How many first-century Jewish people thought it
likely that the Messiah would be God Incarnate, rather than a powerful human king? Mary is not your average Jewess. She's someone in
deep contact with
God more than
any woman
before and
after Her
. Therefore, situations that you consider
likely among average first-century Jews shouldn't automatically apply to Her.
God, the
Most Holy and
Pure One
, came down from Heaven,
a place where unholiness and impurity cannot dwell, and
took form within Her, and thus Her body and spirit had to have already been so Holy and Pure (in part by His doing) to be a Heaven on Earth. God says the
pure in heart will
see Him, and to be pure in heart means to be pure in thought, word, and deed. Therefore, how much
more Pure would Mary have had to be in order to
contain within Her body and spirit God,
the Most Holy and Pure One, and be His
Mother? To the point of being Second only to God? Would God not also want a Spouse and Father of Holiness and Purity for such a Woman as Mary and Her Son (God Incarnate), rather than an average impure male? Do you not think God would bring two holy and pure people together in order to be each other's spouses and parents of God Incarnate?
Whether or not you agree with any of that, after the angel, Gabriel, announced to Mary God's will for Her to bear a Son, and before he explained it'd occur by and with the Holy Spirit (God), Mary asked him how that would happen when She is a virgin. At the time Mary gave that response, She was
already betrothed to Joseph, and if She had
any intention of sexual intercourse with him, at
any point in the future, She
wouldn't have responded like that at all, because a pregnancy would've been the natural result. Therefore, there was no reason for Her to question Gabriel, nor mention that She was a virgin,
unless She had taken a vow of virginity. Since Mary and Joseph were already betrothed at this point, he would've known of Her vow, he never refused Her as a Spouse because of it.