Olivia de Havilland and actress Joan Fontaine, also an Academy Award winner for Suspicion, were sisters. Unfortunately they had a rather adversarial relationship for most of their lives. The trouble between them seems to have had its roots in the way they were treated by their mother, who seems to have been the epitome of a nightmare stage parent. She favoured Olivia, who began acting and achieved success first, over Joan; she even refused to let Joan use their surname- de Havilland- in her career, which is why she went by Fontaine (her mother's maiden name). Resentment and rivalry punctuated the relationship between the sisters, with petty behaviour exhibited by both at various times.
She was active in politics; a Democrat, but unlike so many of the acting community today, not afraid to stand up for what was right, as she did when she stood against Dalton Trumbo, who tried to coerce her into giving an anti-American, pro-Russia speech. Trumbo, a shameless Hollywood communist, referred to the U.S. as a "menace" to Russia, as he was a big fan of Stalin. An account of Olivia's push back against him is given here .