Complex sentence: Brian wasn't revealed to be an atheist until season 7; in fact, in earlier seasons, he was shown to be very much a believer of God, especially in "If I'm Dyin', I'm Lyin'" in season 2.
Split into simpler sentences: Brian wasn't revealed to be an atheist until season 7. In earlier seasons, he was shown to be very much a believer of God especially in "If I'm Dyin', I'm Lyin'" in season 2.