I'm trying to list the closely related keys to C♯ major, and here is what I get:
- C♯ major, the original key
- D♯ minor
- F♯ major
- A♯ minor
- x (B♯ diminished is not a key!)
For the points that have
(???) next to it, I get some keys that are not part of standard usage: E♯ minor and G♯ major. Sometimes I think about turning them into enharmonic equivalents which makes F minor and A♭ major, but they do not seem to fit the definition. Are they close to C♯ major?