Olivia de Havilland and Joan Fontaine were sisters. They were also rivals. Things didn't get as bad as Cain and Abel, but they were notoriously prickly about each other, and by the time De Havilland won her first Oscar for 1946's To Each His Own, they were barely on speaking terms. Fontaine frequently blamed jealousy, especially since the two were nominated against each other in 1941, each for their second nomination...and Joan won:
Apparently, Olivia was less offended by that and more offended by an insulting (but pretty funny) remark Fontaine made about her sister's new husband ("He's had four wives and written one book. Too bad it isn't the other way around."). And one doubts Olivia could have been too shocked by her sister winning: Joan had just starred in the previous year's Best Picture winner and she had won the New York Film Critics' Circle prize.
But then, who knows? Maybe De Havilland was rooting for Bette Davis or even someone else. It is, after all, a lineup full of rich performances:
