Gustav Klimt and Emilie Flöge
During Klimt’s lifetime it was widely assumed that he and Emilie Floge were lovers however that is most likely not the case. The surviving correspondence between the two is voluminous, yet entirely platonic.
Klimt never married but he had many lovers and reportedly fathered somewhere between 3 and 40 illegitimate children. But despite Klimt’s notorious philandering, Emilie remained true to him not only throughout his life, but also thereafter; she also never married. [src] [i]