There have been many rumors that Umberto was unfaithful, or even bisexual, but isn't true
Let's correct this right now!
I know an elderly gentleman who, as a pretty young man, was kept by a Swedish baron. (The Swedish royal family nicknamed him "the little baron".)
He's far too grand, successful, and worldly to be bothered retailing an untruth (had a career in Hollywood, etc), and is a fund of amusing anecdotes given his past -- he's shared some of his personal history on television, but not explicitly!
He told me that he had once been sexually propositioned on the Lido. He turned the man down.
However, a year later at the Savoy Grill in London he was formally introduced to the man, who turned out to be Umberto!
He said the ex-King was very gentlemanly and droll about it.
"I believe young man we have met before" he said.
I bowed very low: "Yes Your Majesty, I believe we have..."
Ironically, he became friendly with Princess Maria Pia, and used to Cha Cha with her!