Dean smiled with a little chuckle when Sam spoke and leaned up the short distance between them to kiss him, his finger teasing a little bit longer before he eased the tip inside, pushing in past the first knuckle and further. It was tight, hot, and not what he expected at all, but he was definitely already imagining how it'd feel, so damn tight around his cock, and it made his breath catch in his throat as he kissed him.
"God damn, Sammy, you're tight," he murmured, rocking his finger in and out slowly for a few moments before he arched it to try to find Sam's prostate. Theoretically, Dean had known of the gland before the whole first-time sex thing, but he hadn't known the pleasure it caused. Now, he wanted to make sure Sam felt every bit of that pleasure.
After a few moments, Dean started to ease a second finger inside, sitting back on his heels to see what he was doing, biting into his lower lip. His free hand curled around Sam's cock, stroking it slowly, and Dean could feel the blush rising on his own skin.