There are Angels and there are Humans and there are Demons.
Sometimes they interbreed, and you get a Nephilm or a demon child.
Sometimes, if a Human is in an Angel line, many generations later an Angel can be born with a 'defect'.
This is very rare, there could be maybe two of these 'defected' Angels in a generation.
And that's who Castiel is. An Angel, with a 'defect'. And that would be alright, if Castiel's 'defect' wasn't something that is a big part of the Angels as a whole.
He doesn't have wings.
He has everything every other Angel has – grace, healing powers, all the rights that come with being a resident of Heaven, the Angel's realm. Just not wings. Meaning he can't fly.
He was bullied about this, and he was barely a part of his family save for living in his home.
He used to despise being Flightless. But something happened a little while ago that made him kind of glad for his lack of wings.
That is where Castiel comes in.
Of course, he has been Flightless all of his life. He is not one of the disgraced Angles who were stripped of their wings and became Human; he is just and Angel without wings. Castiel was tormented by his brothers and classmates for years; every day was taunted in the morning, no friends during school and trying to avoid attention as he went straight to his room at home. His life was pretty much Groundhog day, except for those rare times when he could just go out to the park and walk around. No one stopped him or laughed at him, because they just thought he was a normal Human taking a stroll. Castiel wished he was Human, or that at least he had wings, but no, he thought to himself every day, I have to get the worst luck of them all.
When he got to school, Castiel was always careful to avoid walking anywhere near any Angels or Demons. He generally avoided most Humans as well, but he had found that they were slightly less judging about his missing wings and so he felt comfortable just walking past them and not making eye contact.
One of the tiring school days Castiel decided he just couldn't take it anymore. The taunts were just too much and he left that very day. He walked two miles from the heart of the town and found himself skirting the edge of his home.
He walked straight past his own home and headed further away from the jeers that had followed him all of his life. Soon enough he came across a junk yard, filled with rusting carsand weeds and at the back of the junk yard there was an abandoned house, barley standing, Castiel thought.
He went in. Good job he did, too. There, that house, was where Castiel met the most meaningful someone he would ever meet.
Ever.