Only years in which 2 or more performers in the same film nominated for Best Actor or for Best Actress and one of them won:
Two or more actors have been nominated as Best Actor for the same film 12 times [1935, 1944, 1961, 1953, 1956, 1958, 1964, 1969, 1972, 1976, 1983 and 1984].
One of them has won for that film only 4 times:
1944 -- Bing Crosby for Going My Way
1961 -- Maximilian Schell for Judgment at Nuremberg
1976 -- Peter Finch for Network
1984 -- F. Murray Abraham for Amadeus

Two or more actresses have been nominated as Best Actress for the same film 5 times [1950, 1959, 1977, 1983 and 1991].
One of them has won for that film only once:
1983 -- Shirley MacLaine for Terms of Endearment