Gloria has been quite open about her relationship with Ole Blue Eyes, even talking about him in her book and in her recent documentary. While she has had a very long list of famous lovers, it was Mr. Sinatra which she spoke of very often. In a recent appearance on Watch What Happens Live with host Andy Cohen, she said "He was a wonderful friend and an absolutely extraordinary person in my life."
The Princess of Monaco met Mr. Sinatra when they acted together in High Society where their characters fell for each other. While it was never confirmed that the two officially went out, a close friend of Frank, George Jacobs, said in an interview with CBS The Early Show that they did date.
The Lauren Bacall-Frank Sinatra was allegedly due to Lauren's at the time husband, Humphrey Bogart, having an affair with his secretary. They then went public with the relationship after her husband died but it ended soon after.