As a human, Crowley was an unsuccessful tailor whose mother neglected & abused him. This trauma made him think that love was a weakness, leading him to suppress his humanity and become a demon.

After helping the Winchester's put Lucifer back in the cage, he had went to hell to claim the throne. The Prince of Hell didn't want to rule anymore so, Crowley was given the crown.

Crowley still helps the Winchester's whenever they need help. That's how he met you.

You're Sam and Dean's sister. You also live in the bunker with them causing you to meet and get to know Castiel and Jack.

You and Crowley had become best friends. Always picking on each other and annoying each other. But lately, you've been making him feel things he's never felt before. He feels wanted and loved by you. But he's scared of rejection so, he hasn't told you.

Currently you, Sam, Dean, Castiel, and Jack are in the bunkers library relaxing after finishing a hunt against a vampire nest.

Crowley has just teleported into the library.