I’m compiling a list for something I’m writing. I’m not interested in the ones about whom there were gay rumors but no proof (Cary Grant, Tom Cruise, etc.) but the ones who either discussed/admitted their homosexuality, were involved in same sex scandals, left letters that are pretty good indicators, etc., or otherwise were pretty surely at very least actively bisexual.
A few that I can think of offhand:
Cole “De Lovely” Porter
Elton John
Will Geer
Alec Guinness (whether he was regularly gay or not, he was definitely arrested at least once for soliciting a male prostitute)
Tony Perkins
Rock Hudson
Alexander Hamilton
Alexander the Great
Eleanor Roosevelt
Gloria Morgan Vanderbilt (mother of the designer- famous in her own time as a socialite)
Thomas Mann (indisputably bisexual but disowned one of his sons for being openly [and exclusively] gay)
Oscar Wilde
John Cheever
King James (VI of Scotland and I of England), the son of Mary Queen of Scots, married Princess Anne of Denmark but was rumoured to be far more enamoured of his best friend George Villiers, the Duke of Buckingham.
Angelina Jolie talks about her bisexuality quite often, and she was married to Billy Bob. Anne Heche was involved with Ellen DeGeneres before marrying a guy. I think that counts as bisexual.
Yukio Mishima was bisexual. He had a wife and two (?) children, but had a steady male lover–who ended up being the one to help him invade and commit seppuku in the military headquarters of Japan’s Self Defense Force.
There has been some credible evidence that Eleanor had a relationship with noted lesbian journalist Lorena Hickok, but I don’t know if it’s ever been substantially proven.
It is fairly widely accepted that economist John Maynard Keynes is an exceedingly rare example of a man who was almost exclusively homosexual (including a seven-year relationship with painter Grant Duncan) in his younger years, and yet went on to a happy marriage to a woman.