He has appeared in diverse roles since his first lead role in 1999 's October Sky , followed by the 2001 cult hit Donnie Darko , in which he played a psychologically troubled teen and onscreen brother to his real-life sister , actress Maggie Gyllenhaal . He has appeared in diverse roles since his first lead role in 1999 's October Sky , followed by the 2001 indie cult hit Donnie Darko , in which he played a psychologically troubled teen and onscreen brother to his real-life sister , actress Maggie Gyllenhaal .