Perpetual virginity of Mary

Scott Hahn's reply

Scott Hahn's commentary on the gospel of Matthew:

Four observations support the Church's tradition:

These brethren are never called the children of Mary, although Jesus himself is (Jn 2:1; 19:25; Acts 1:14).
Two names mentioned, James and Joseph, are sons of a different "Mary" in Mt 27:56 (Mk 15:40).
It is unlikely that Jesus would entrust his Mother to the Apostle John at his Crucifixion if she had other natural sons to care for her (Jn 19:26-27).
The word "brethren" (Gk. adelphoi ) has a broader meaning than blood brothers. Since ancient Hebrew had no word for "cousin", it was customary to use "brethren" in the Bible for relationships other than blood brothers. In the Greek OT, a "brother" can be a nearly related cousin (1 Chron 23:21-22), a more remote kinsman (Deut 23:7; 2 Kings 10:13-14), an uncle or a nephew (Gen 13:8), or the relation between men bound by covenant (2 Sam 1:26; cf. 1 Sam 18:3).
Continuing this OT tradition, the NT often uses "brother" or "brethren" in this wider sense. Paul uses it as a synonym for his Israelite kinsmen in Rom 9:3. It also denotes biologically unrelated Christians in the New Covenant family of God (Rom 8:29; 12:1; Col 1:2; Heb 2:11; Jas 1:2; CCC 500).

Wikipedia. The apocryphal gospel of James preserves this belief of the early church.
Not a "teaching found explicitly in the Bible." But there are other teachings not found explicitly and literally in the Bible:
- "All true Christian teachings must be written in the Bible" is not a teaching written in the Bible.
- "The Bible" never uses the word "Bible" to mean what we mean by the word: "a combination of both Old and New Testament Scriptures."
- The list of books that are to be treated as "the Word of God" are not listed by any of the books of the Bible.
Acts 8:40 ... he preached until he came to Cesarea.