Close My Eyes (1991)

A woman, Natalie (Saskia Reeves), becomes reaquainted with her younger brother, Richard (Clive Owen), from whom she was separated as a child. They meet on and off, intermittently for the next few years, until the sister gets married to Sinclair (Alan Rickman), a wealthy businessman. Once married, the siblings become attracted to each other physically and start a sexual relationship which blossoms into love, especially on the part of the brother. Everything comes to a head when Sinclair suspects Natalie is having an affair, but does not know with whom. He arranges for them to move to America and, at their going away party, the truth comes out.