A/b/o angst fic refused mating gift. Found. In comments!
It's been so long I cant remember if its j2 or Sam/Dean (I think it's Sam/Dean?). It's Sam 18th birthday or graduation party. They are expected to be mates, and accepting Dean's mating gift is part of the protocol. When Sam gets to it in the gift queue, he sets it aside and doesn't open it because he wants to go to Stanford and is afraid Dean, as his alpha, won't let him. Much angst ensues. It ends eith Sam opening the gift and it's Stanford student IDs for both of them. Thanks!