History of the wings

The wings that you have is the opposite color of your soulmates wings.

For example;
Black and white go together.

When you meet your soulmate you just know it and it's the best feeling in the world.

John felt that way with Mary. They both died unfortunately and they were buried.

So, Dean and Sam are on there own.

When you turn 16 you first get your wings.

Dean is turning 16 and so is Castiel.

Dean doesn't know Castiel exists and Castiel doesn't know Dean exists.

That is until Castiel gets transferred to Dean's school.