Mary was a virgin so yes she asked how would she have a son. But the fact that Jesus had named brothers and unnamed sisters suggests she had relations with her lawful husband "after" Jesus was born.
And that's strongly implied if not outright stated.
4 When Joseph woke up, he did what the angel of the Lord had commanded him and took Mary home as his wife. 25 But he did not consummate their marriage until she gave birth to a son. And he gave him the name Jesus.
2 Samuel 6:23 tells us: Therefore Michal the daughter of Saul had no child UNTIL the day of her death.
Are we to assume that Michal had children after she died?
Until only states that they had no relation up to that point, the Bible does not say they had sex ever, before or after that point!
Lk 1:34 no sex ever!
Martin Luther
It is an article of faith that Mary is Mother of the Lord and still a virgin. … Christ, we believe, came forth from a womb left perfectly intact. (Weimer’s The Works of Luther, English translation by Pelikan, Concordia, St. Louis, v. 11, pp. 319-320; v. 6. p. 510.)
John Calvin
(On the Heretic Helvidius) Helvidius displayed excessive ignorance in concluding that Mary must have had many sons, because Christ’s “brothers” are sometimes mentioned. (Harmony of Matthew, Mark and Luke, sec. 39 [Geneva, 1562], vol. 2 / From Calvin’s Commentaries, translated by William Pringle, Grand Rapids, Michigan: Eerdmans, 1949, p.215; on Matthew 13:55)
[On Matt 1:25:] The inference he [Helvidius] drew from it was, that Mary remained a virgin no longer than till her first birth, and that afterwards she had other children by her husband . . . No just and well-grounded inference can be drawn from these words . . . as to what took place after the birth of Christ. He is called “first-born”; but it is for the sole purpose of informing us that he was born of a virgin . . . What took place afterwards the historian does not inform us . . . No man will obstinately keep up the argument, except from an extreme fondness for disputation. (Pringle, ibid., vol. I, p. 107)
Under the word “brethren” the Hebrews include all cousins and other relations, whatever may be the degree of affinity. (Pringle, ibid., vol. I, p. 283 / Commentary on John, [7:3])
John Wesley
‘I believe that He [Jesus] was made man, joining the human nature with the divine in one person; being conceived by the singular operation of the Holy Ghost, and born of the blessed Virgin Mary, who, as well after as before she brought Him forth, continued a pure and unspotted virgin’ (‘Letter to a Roman Catholic’, The Works of Rev. John Wesley, vol 10, p. 81).
St Augustine, Sermons 186.1 (early 5th century):
“In being born of a Virgin who chose to remain a Virgin even before she knew who was to be born of her, Christ wanted to approve virginity rather than to impose it. And he wanted virginity to be of free choice even in that woman in whom he took upon himself the form of a slave” (Holy Virginity 4:4 [A.D. 401]).
“It was not the visible sun, but its invisible Creator who consecrated this day for us, when the Virgin Mother, fertile of womb and integral in her virginity, brought him forth, made visible for us, by whom, when he was invisible, she too was created. A Virgin conceiving, a Virgin bearing, a Virgin pregnant, a Virgin bringing forth, a Virgin perpetual. Why do you wonder at this, O man?” (Sermons 186:1 [A.D. 411]).
“Heretics called Antidicomarites are those who contradict the perpetual virginity of Mary and affirm that after Christ was born she was joined as one with her husband” (Heresies 56 [A.D. 428]).