Cis-Dur
Its relative major is E major. Its parallel major, C-sharp major, is usually replaced by D-flat major, since C-sharp major’s key signature with seven sharps is not normally used. Its enharmonic equivalent, D-flat minor, having eight flats, including the B, has a similar problem. Therefore, C-sharp minor is often used as the parallel minor for D-flat major. (The same enharmonic situation occurs with the keys of A-flat major and G-sharp minor.)