Joan Fontaine won best actress in 1942 (Suspicion) while her elder sister Olivia de Havilland won for best actress in 1947 (To Each His Own) and in 1950 (The Heiress). They are the only siblings to win Academy Awards for acting.

Julie Christie won an Academy Award for best actress in 1966 (Darling). Her brother Clive is a university professor and not an actor.

Peter Fonda was nominated but did not win an Academy Award for best actor in 1998 (Ulee's Gold) while his sister Jane won an Academy Award for best actress in 1972 (Klute) and 1979 (Coming Home).

Ben Affleck won Academy Awards for writing in 1998 (Good Will Hunting) and producing in 2013 (Argo) while his brother Casey has won an Academy Award" for best actor in 2017 (Manchester by the Sea).

More Info: www.wikipedia.org