Ok, another clue for #1:
There's a stage musical and movie made about them.
And because no one has got it yet, I'm adding another ...
There have been only about a dozen artists who have had posthumous UK number 1 hits. But one of those hits actually knocked another posthumous hit off the top spot - name either artist.
And for an extra hint, the 2nd song was subject of a lawsuit and found to have plagiarized another tune, name THAT song and artist.