I know many of the replies to protestants objections of this, but here are some of their replies to the Catholic refutations:
When you tell them that Jesus entrusted Mary to Johns care they say that would be appropriate in light of His earlier teaching on who His real mother and brothers are in which case they say James at that time was not His real brother since He did not believe and then when you say noone but Jesus was mentioned at the temple their response is that that is not surprising since the point of the story has nothing to do with his brothers, so it doesn’t need to be mentioned. What is your response to that?
I am always amazed when Protestants question the perpetual viginity of Mary especially when all the founding fathers of Protestantism believed in it. Even John Wesley who founded Methodism believed in Mary’s perpetual virginity.
Luther:
Christ, our Savior, was the real and natural fruit of Mary’s virginal womb . . . This was without the cooperation of a man, and she remained a virgin after that.
{Luther’s Works, eds. Jaroslav Pelikan (vols. 1-30) & Helmut T. Lehmann (vols. 31-55), St. Louis: Concordia Pub. House (vols. 1-30); Philadelphia: Fortress Press (vols. 31-55), 1955, v.22:23 / Sermons on John, chaps. 1-4 (1539) }
Christ . . . was the only Son of Mary, and the Virgin Mary bore no children besides Him . . . I am inclined to agree with those who declare that ‘brothers’ really mean ‘cousins’ here, for Holy Writ and the Jews always call cousins brothers.
{Pelikan, ibid., v.22:214-15 / Sermons on John, chaps. 1-4 (1539) }
A new lie about me is being circulated. I am supposed to have preached and written that Mary, the mother of God, was not a virgin either before or after the birth of Christ . . .
{Pelikan, ibid.,v.45:199 / That Jesus Christ was Born a Jew (1523) }
Scripture does not say or indicate that she later lost her virginity . . .
When Matthew [1:25] says that Joseph did not know Mary carnally until she had brought forth her son, it does not follow that he knew her subsequently; on the contrary, it means that he never did know her . . . This babble . . . is without justification . . . he has neither noticed nor paid any attention to either Scripture or the common idiom.
{Pelikan, ibid.,v.45:206,212-3 / That Jesus Christ was Born a Jew (1523) }
Editor Jaroslav Pelikan (Lutheran) adds:
Luther . . . does not even consider the possibility that Mary might have had other children than Jesus. This is consistent with his lifelong acceptance of the idea of the perpetual virginity of Mary.
{Pelikan, ibid.,v.22:214-5}
“. . . she is full of grace, proclaimed to be entirely without sin. . . . God’s grace fills her with everything good and makes her devoid of all evil. . . . God is with her, meaning that all she did or left undone is divine and the action of God in her. Moreover, God guarded and protected her from all that might be hurtful to her.”
Ref: Luther’s Works, American edition, vol. 43, p. 40, ed. H. Lehmann, Fortress, 1968
“. . . she is rightly called not only the mother of the man, but also the Mother of God. . . . it is certain that Mary is the Mother of the real and true God.”
Ref: Sermon on John 14. 16: Luther’s Works (St. Louis, ed. Jaroslav, Pelican, Concordia. vol. 24. p. 107)
“Christ our Savior was the real and natural fruit of Mary’s virginal womb. . . . This was without the cooperation of a man, and she remained a virgin after that.”
(REf: On the Gospel of St. John: Luther’s Works, vol. 22. p. 23, ed. Jaroslav Pelican, Concordia, 1957)
Calvin:
Helvidius displayed excessive ignorance in concluding that Mary must have had many sons, because Christ’s ‘brothers’ are sometimes mentioned.
{Harmony of Matthew, Mark & Luke, sec. 39 (Geneva, 1562), vol. 2 / From Calvin’s Commentaries, tr. William Pringle, Grand Rapids, MI: 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) }