The answer was so soft, Castiel could tell Dean nearly missed it.
"I can't." Castiel could feel tears pooling in his eyes, and could see Dean's eyes shine as well.
"You what?" Dean whispered.
"I can't, Dean, I'm sorry, I can't," Castiel gasped out through the sobs that began ripping through his chest. God, this hurt so much more than he thought possible. He wanted Dean. He wanted him so damn bad, but he couldn't marry him. His father would kill him and then take out his anger on his mother and him, and probably even go after Dean, and Castiel wouldn't let that happen, especially when he barely deserved Dean.
"What do you mean you can't?" Dean asked, voice wavering, hands trembling. He looked so god damn broken, so defeated, and it just made him sob harder.
"M-my dad…he'll…." He began, but Dean cut him off.
"No. No! Don't think like that! It-it'll be okay, I promise!" Dean said, tears spilling down his cheeks.
"No, Dean! I don't deserve you! I don't deserve you and I don't deserve what you've given me!" Cas cried, and damn if that wasn't half the truth.
"Don't you dare say that!" Dean yelled. Castiel flinched back. "You deserve the world! You deserve happiness and love and so much more! Now maybe I can't give that to you, or maybe I haven't given it to you enough, but dammit Cas, you deserve to be happy! You deserve to get something you want! Maybe you don't want me, but you at least need to be happy!" Dean screamed.
"I don't deserve you! Of course I want you! I just shouldn't get you!" Castiel screamed back.
"No! You don't get to leave me! You don't get to! Don't you understand that?"
"WHY?!" Castiel yelled.
"BECAUSE YOU'RE MINE!" Dean screamed. Castiel froze, looking into Dean's agonized green eyes. "You're mine and I won't let you," Dean whispered. "I love you. Please." Dean begged. Dean Winchester didn't beg for anything and dammit that made this so much harder. Castiel sank to his knees, sobs wracking his body. That made it impossible to leave. He'd never been somebody's mine before. Strong arms wrapped around his body.
"It's okay, Cas, it's okay," Dean whispered, and Castiel could hear tears in his voice. Dean gently took his chin, and turned him to face him. "I love you, Castiel Novak, and I will not let you leave me." Dean kissed him softly, and then tilted his face down, taking Castiel's left hand. Castiel let Dean slide the ring onto his finger, and somehow, right there, it felt as if it had always been there.
"I love you too, D-Dean," Castiel whispered, wrapping his arms around Dean's waist. Dean rocked them slowly, his ring on his own finger, and began to sing softly in Castiel's ear.
"I'm lying alone, with the head on the phone thinking of you 'till it hurts….I know you're hurt too, but what else can we do…tormented and torn apart…..I wish I could carry your smile in my heart…for times when my life seems so low….it would make me believe…..what tomorrow could bring….when today doesn't really know….doesn't really know….I'm all out of love, I'm so lost without you….I know you were right, believing for so long….I'm all out of love, what am I without you…I can't be too late to say I was so wrong…."
Castiel let his head fall against Dean's chest, listening to the steady beat of his heart, and sometimes he thought it was the most steady thing in his life.
"It's okay, Cas, I'm here. I'm going to fix this. We're going to be okay," Dean whispered. And Castiel knew they would be okay. Because that's what Dean did.
He fixed things.