The key of G major uses one sharp: F#. The chords in G major are: G maj, A min, B min, C maj, D maj, E min, F# diminished. The relative minor is E minor.
Gb Major has 6 flats: Bb, Eb, Ab, Db, Gb, Cb. The relative minor of Gb Major is Eb minor. Gb Major is tonally identical to and can be referred to as F# Major.
