Disclaimer: Do not own.
This story will mostly be about Crowley dealing with raising a half human Spawn with the help of the Winchester boys, but I figured a little Bobby/Crowley wouldn't go amiss to help explain their adorable relationship.
Love
Demons don't love.
That isn't to say that they can't.
Bobby knew that better than any human alive he reckoned. Because even though Crowley never said it, Bobby knew.
He knew, because when he whispered "I love you", into the darkness of his room, arms tight around the Demon, Crowley didn't answer.
xxx
Demons can love.
They just choose not to.
They do, in fact, regularly love a great deal of things, but in the context of romantic entanglements, love is not a term ever bandied about, because to love another person was to invite disaster upon yourself.
But Crowley did love, but he would not admit to it, except that he did. Every single time he did not refute Bobby's declaration.