This song by Richard Marx is in C.
The chords in brackets are transitional.
These are the “cheat” chords I played…
Part 1a: C2 - F2
Part 1b(i): Dm7 - F/G
Part 1b(ii): Dm7 - G/B
Part 2a: Am7 - Dm7
Part 2b: Am7 - Dm7 - F/G
Part 3a: C2 - G - Am7 - F2 - F/G
Part 3b: same as 3a
Part [...]



