I think that was Lester Chambers, who it seems barely saw any royalties from his one big hit.
The only bad thing I heard about Sly was that he was busted for having a piece in a nightclub in Ft. Myers, FL (iirc). Or some such.
https://nypost.com/2011/09/25/funk-legend-sly-stone-homeless-and-living-in-a-van-in-la/