This argument feels strong because it sounds like common sense. But common sense is not exegesis, and the “plain reading” turns out to depend on ignorance of Greek, ignorance of the Septuagint, and above all ignorance of what the Gospels themselves say about who these “brothers” are and who their mother is.

The entire Protestant argument stands or falls on the assumption that the Greek word adelphos means “biological brother born of the same mother.” It often does — James and John, the sons of Zebedee, are called adelphoi and they are biological brothers. No one disputes that the word can mean biological sibling. The question is whether it must mean biological sibling in every instance. It demonstrably does not. In Koine Greek — and especially in the Septuagint, the Greek Old Testament that Jesus and the apostles actually used — adelphos covers brothers, half-brothers, stepbrothers, cousins, nephews, kinsmen, and even close associates. The reason is simple: Hebrew and Aramaic have no dedicated word for “cousin.” The Hebrew word ach covers all male relatives, and the Septuagint consistently translates this broad kinship term as adelphos.

The proof is in the Bible itself. In Genesis 14:14, the Septuagint calls Lot Abraham’s adelphos (“brother”). But Genesis 11:27 makes clear that Lot is Abraham’s nephew — the son of Abraham’s brother Haran. In Genesis 29:15, Laban calls Jacob his adelphos, but Jacob is Laban’s nephew. If adelphos must mean biological brother in the Gospels, then Abraham and Lot are biological brothers — which they demonstrably are not.

The most devastating evidence against the Protestant reading comes not from linguistics but from the Gospels themselves. The “brothers of Jesus” — specifically James and Joseph, the first two named — are identified by the Gospel writers as the sons of a different Mary. This is not inference. It is explicit.

The critical move is at the cross. Three of the four Gospels name the women present at the crucifixion, and the lists are revealing:

Now compare these names with the “brothers of Jesus” list from Matthew 13:55: “James and Joseph and Simon and Judas.” James and Joseph — the first two “brothers” — are explicitly identified at the cross as sons of “the other Mary,” not of the Virgin Mary. Matthew and Mark both name this woman and both identify her children, and she is a different person from Jesus’ mother.

Two of the four are positively identified as sons of a different Mary. The other two are never identified as sons of the Virgin Mary anywhere in Scripture. The Protestant case requires a positive identification that does not exist.

The text Protestants lean on hardest is Galatians 1:19, where Paul writes: “I saw none of the other apostles except James the Lord’s brother.” This sounds definitive. But two things must be noted.

First, Paul uses adelphos throughout his letters for all fellow Christians — “brothers and sisters in Christ.” The word does not carry a special biological marker in Paul’s usage.

Second, this same James is identified in the apostolic lists as “James the son of Alphaeus” (Matt 10:3, Mark 3:18, Luke 6:15, Acts 1:13). Alphaeus and Clopas are widely held by scholars to be the same person — different transliterations of the Aramaic name Halpai — though the identification is not proven beyond dispute. But even without it, the cross-reference evidence from Section III stands on its own: the mother of James and Joseph is identified at the cross as a different Mary, regardless of what we call her husband.

Matthew 1:25 says Joseph “knew her not until (heos hou) she had given birth to a son.” The Protestant reads “until” as implying a change: he didn’t know her before, therefore he did know her after. But biblical Greek does not work this way. Heos hou describes the state of affairs up to a stated point without implying anything about what happens afterward.

In every case, “until” describes what was the case up to a stated moment and makes no claim about what happened after. Matthew 1:25 is telling you one thing: Joseph did not have relations with Mary before the birth. It says nothing about afterward. Reading it as “he did know her after” is importing modern English assumptions into ancient Greek.

In John 19:26–27, Jesus on the cross entrusts Mary to the beloved disciple: “Woman, behold your son… Behold your mother.” And from that hour the disciple took her into his own home.

If Mary had four or more biological sons alive — James, Joseph, Simon, and Judas — this act would be a shocking insult. Under Jewish custom, the care of a widowed mother was a sacred obligation falling to her sons. Bypassing her own children to entrust her to a non-relative would be a public disgrace to the family. No Jewish son would do this, and no Gospel writer would record it approvingly, unless there were no other sons.

Perhaps the most uncomfortable fact for modern Protestants is that their own spiritual fathers — the men who launched the Reformation — affirmed Mary’s perpetual virginity without hesitation.

Luther affirmed it from 1523 to his final sermon in 1546. Zwingli called Mary “ever chaste, immaculate.” Calvin mocked the denial of her perpetual virginity as “excessive ignorance.” And these were not merely individual opinions. The Schmalkald Articles (1537), a foundational Lutheran confessional document, call Mary “ever-virgin.” The Second Helvetic Confession (1566), Chapter 11, confesses that Christ was “born of the blessed and ever virgin Mary” (semper virgine Maria). The Geneva Bible’s own notes affirm it. The denial of Mary’s perpetual virginity is not a Reformation position. It is a post-Reformation innovation, adopted by later Protestants who unknowingly departed from their own founders.