雅兄 is read as がけい (gakei) and means you.
がけい
gakei
ががく
old Japanese court music
がち
artistry
がぶん
elegant (literary) style
がごう
alias
がじん
individual of taste
がげん
elegant words
うたのすけ
first assistant court musician (ritsuryō system)
うたのかみ
chief court musician (ritsuryō system)
みやびお
elegant and refined man
がご
classical poetic language (esp. of the Heian period)
がみ
high class
うたのさかん
alternate assistant court musician (ritsuryō system)