Calliope

Five human characters in Neil Gaiman's The Sandman become creative successes:

Orpheus, singer/song-writer, is the son of Dream and Calliope;
William Shakespeare, playwright, makes a deal with Dream;
Ric Madoc, novelist, imprisons Calliope;
Hal Carter, comedian, was affected by a dream;
Foxglove, singer/song-writer, met Dream - and stops performing after meeting Death.

And maybe there is another somewhere? But five is a big number. As usual, the list grew in being written. I wasn't counting Orpheus but, despite his immortal parentage, he is described as human and mortal. Of course, like Hob Gadling, he loses his mortality through making a deal but that is another matter.