Complex sentence: His best friend, Yale Pollack (Michael Murphy), married to Emily (Anne Byrne), is having an affair with Mary Wilkie (Diane Keaton); her ex-husband and former teacher, Jeremiah (Wallace Shawn), also appears.
Split into simpler sentences: His best friend, Yale Pollack (Michael Murphy), married to Emily (Anne Byrne), is having an affair with Mary Wilkie (Diane Keaton). Mary's ex-husband and former teacher, Jeremiah (Wallace Shawn), also appears.