Despite being younger than you, Dean has always been protective over you. Yes, you are his older sister but he also knows you are not invincible. He also knows you dealt with much worse from John than he did. Even as you both grow up, that protectiveness stays.

Which is why he is always vigilant of every interaction you have with Castiel. Lately he’s noticed the two of you have become more close. Castiel is staying around more often, showing up at random, he’s also always asking Dean about you. Dean can’t help but be wary of Castiel’s intentions around you.

Yes, he trusts Castiel. The angel has helped them with so much over the years and he would call him one of his best friends. But this is about your heart and he knows how fragile you are. Like hell will he let Castiel break your heart.

But Dean never gets the chance to bring up his concerns. A hunt the three of you were on went sideways, Castiel immediately stepping in to protect you while not realizing what you were up against. By the time you got back to the motel safely it was just you, Dean and Castiel’s trenchcoat. But no Castiel.

Days go by and yet you still refuse to accept what happened. Dean hasn’t seen you let go of the trenchcoat once, your hands constantly clutching at the fabric. You rarely ever go to your bedroom anymore, constantly in the library of the bunker. Dean has found you pouring over every book they have, desperately searching for some way to bring Castiel back.

At night it’s worse. Dean hears your soft sobs from the library every night, your screams when you wake up from nightmares. But the most heartbreaking thing is hearing your prayers. Every single night he hears you praying to Castiel, even just simply telling him how your day was. The sobs that follow when you get no answer always make his chest hurt.

So one night he finally has enough. When he walks into the library to check on you he finds you passed out in one of the chairs, almost falling out of it. He quickly strides over and picks you up in his arms, adjusting to tuck your head into his shoulder. His fingers skin across your back trying to soothe you as you stir.

“Shh, it’s okay sweetheart. Just go back to sleep.” Dean murmurs gently to you trying to keep you asleep. He just wants to take you to his room so you can sleep in a bed for once.