As an omega, Castiel is ineligible for the throne after his father dies. When his uncle takes the crown, Metatron's first order of business is to arrange a betrothal with King John for the hand of his firstborn son, the Crown Prince of Terra.
So Castiel flees.
On his first night on the run, Castiel stumbles into a band of outlaws just at the border. Injured and wary, he has no choice to stay with them. And although he had planned to return to his own kingdom once it was safe, home might not be the place he left, but instead with Dean, their alpha leader that took him in.
Dean refused to look up his soulmate. His parents ran into each other by chance. Karen stopped by Bobby’s garage after her car unexpectedly broke down. Sam got seated next to Eileen on a plane, and he spent two hours miming conversation before she admitted she read lips.
Was it stupid for Dean to hold out for a story like that? Probably.
But he doesn’t regret his decision - not until Castiel Novak wanders into his tattoo parlor, asking about a cover up for his soulmark.
While Mary was alive, she would tell Dean that soulmates were chosen by angels. When the right time came, he would hear his soulmate’s voice in his head, and he would know, wherever they were, they were singing just for him.
But Dean never heard a damn thing. Not at 12, when most people heard their first soul song. Not at 15, when Sammy heard his. Not at 17, when only two-percent of the population heard their first.
And definitely not at 28, when Sam leaves to be with the love of his life, and Castiel, deaf professor of rock music history at KU, moves in.