[guitarplayer1953]

Do you not mean fact that goes against traditions?
If this is an accident how many more are there?
Maybe it is a accident of translation that says to some that Peter is #1.
In Gal 2:9 Paul names James first as should be since he is the brother of Jesus.

[Petronski]

Translation of the OT from the Hebrew to the Koine Greek noted that there is no Hebrew word for cousin, close relative, uncle, etc. Thus the word for brother (adelphos) was used.

The writers of the NT followed the pattern, using adelphos whenever the recollection from Greek, Hebrew or Aramaic was a reference to a cousin, close relative, uncle, etc. was meant.

Accident of translation.

[Petronski]

Gal 2:9 James, and Cephas, and John. No proof of any greater authority can be drawn from the placing or numbering of James first, which perhaps St. Paul might do, because of the great respect he knew the Jewish converts had for St. James, bishop of Jerusalem, where the ceremonies of the law of Moses were still observed. Several Greek copies have Peter, James, and John. So we also read in St. Jerome's Commentary, p. 240, and St. John Chrysostom in his Exposition, p. 729, has Cephas, John, and James. (Witham)