Three mss. give the title Γρηγορίω ἐπισκόπῳ καὶ ἀδελφῷ, but, as is pointed out by the Ben. Ed., the letter itself is hardly one which would be written to one with the responsibilities of a bishop.  Basil seems to regard his brother as at liberty to come and help him at Cæsarea.  Gregory’s consecration to the see of Nyssa is placed in 372, when his reluctance had to be overcome by force.  cf. Letter ccxxv.  On the extraordinary circumstance of his well meant but futile forgery of the name of his namesake and uncle, bishop of an unknown see, vide Prolegom.