When Dean’s little brother gets taken away, he’s expecting the fight that ensues. He’s expecting the stress that comes from separation, expecting to do all he can to get Sammy back from whatever awful foster family he’s been placed with. He’s not expecting Castiel Novak.
(Castiel, in turn, isn’t expecting his first foster child - five years old and angry - to be the one that leads him to the family he’s always wanted, but life has a funny way of working itself out).
Love never dies a natural death. It dies because we don’t know how to replenish its source. It dies of blindness and errors and betrayals. It dies of illness and wounds; it dies of weariness, of witherings, of tarnishings.