1. - Corey Feldman, The Goonies, 1984. Haim lost Mouth to Feldman - just as, four years later, Feldman lost Les in License To Drive to Haim. After appearing together in The Lost Boys, 1986, The Two Coreys became close friends and (mysteriously) the highest-paid teens and princes, if not kings of the US box-office through seven 80s/90s movies.
2. - Chris O'Donnell, Batman Forever, 1994.