If Mary was a virgin, how did Jesus have brothers?

Take it up with the pope.

Excerpts from here (I would trust the Greek Orthodox Church to understand Greek): https://www.goarch.org/-/the-ever-virginity-of-the-mother-of-god

There are several questions based on Scripture that are often raised by those skeptical about the doctrine of ever-virginity. The first of these involves the passages which state explicitly that the Lord had "brothers." There are nine such passages: Matthew 12:46-47 and 13:55-56; Mark 3:31-32 and 6:3; Luke 8:19-20; John 2:12 and 7:3-5; Acts 1:14; and 1-Corinthians 9:5. The Greek word used in all these passages and generally translated "brother" is adelphos.

The Septuagint, the ancient Greek translation of the Hebrew Scriptures used by the Apostles (abbreviated LXX) includes specific words for "cousin," notably adelphinos and anepsios, but they are rarely used. The less specific word adelphos, which can mean "brother," "cousin," "kinsman," "fellow believer," or "fellow countryman," is used consistently throughout the LXX, even when cousin or kinsman is clearly the relation described (such as in Genesis 14:14, 16; 29:12; Leviticus 25:49; Jeremiah 32:8, 9, 12; Tobit 7:2; etc.). Lot, for instance, who was the nephew of Abraham (cf. Genesis 11:27-31), is called his brother in Genesis 13:8 and 11:14-16. The point is that the commonly used Greek word for a male relative, adelphos, can be translated "cousin" or "brother" if no specific family relation is indicated.

Is there anywhere a clear statement in the Scriptures establishing Jesus brothers as literally the children of Mary? In fact, there is not. Nowhere is Mary explicitly stated to be the mother of Jesus' brothers. The formula for speaking of the Lord's family is "His mother and His brothers." In Mark the possessive, anavtou"of Him," is inserted before both "His mother" and "His brothers," making a clear distinction. In Acts 1:14, the separation is more pronounced: "Mary the mother of Jesus, and His brothers." Some manuscripts use the conjunctive syn "along with, in company with," so that the text reads "Mary the mother of Jesus, along with His brothers." In any case, Mary is never identified as the mother of Jesus' brothers (nor they as her children), but only as the Mother of Jesus.

Another objection to the idea of Mary's perpetual virginity is that the Scriptures use the word "until" or "till" in Matthew 1:25 ". . . and [Joseph] did not know her till she had brought forth her firstborn Son." Whereas in English the word "until" necessarily indicates change after the fact, in the ancient languages of the Bible this is simply not the case. For instance, if we read Deuteronomy 34:6, 2 Samuel 6:23, Psalm 72:7 and 110:1 (as interpreted by Jesus in Matthew 22:42-46), Matthew 11:23 and 28:20, Romans 8:22, and 1 Timothy 4:13, to reference just a few examples, we will see that in none of these passages does the word "until" indicate a necessary change. If it did, then apparently among other things we would be meant to understand that Jesus will at some point stop sitting at the right hand of the Father, and that on some unhappy date in the future He intends to abandon the Church! The use of "until" in Matthew 1:25, then, is purely to indicate that Christ was incarnate of the Holy Spirit and the Virgin Mary, not conceived by Joseph and Mary, since they did not "know" each other "until" the birth. In this context "until" is really synonymous with "before." If on the contrary it were meant in its full contemporary English sense. That is, if it really meant that Joseph and Mary's chaste relationship changed after the birth then the stylistics present another big problem: the reader would have to believe that Matthew was actually inviting contemplation of the couple's later sexual activity. This is doubtful to say the least.

Protestants also believe women can be ordained so that should tell you all you need to know.

No, but they mythologize virginity in a way that Protestants don't. Mary is special to them because she gave virgin birth and then stayed a virgin.

Catholics are deeply invested in that Madonna-Whore complex. It's kind of the basis of their whole religion.

Source: whoring it up at catholic school

Mary could have had kids after Jesus

It's a silly and unnecessary valorization of virginity because marrital s*x is not sinful and would not have made Mary any the lesser. This is why Prots believe Mary and Joseph had a normal, healthy marriage.

Not much choice. Mary was built for that BYC (big yhwh peepee). He could never compete.

He was a cuck and god was the bull