Sam should have seen it coming when Dean smashed his ice cream cone against his face. He should have seen it coming when he coaxed him into the ice cream shop and tried to consult him on what flavor to get, wordlessly telling him what he planned to do. Sam just thought that Dean was being a little considerate of what his mouth would taste like when he ended up kissing him later.
When he planted his lips on Sam’s, his tongue felt like a stranger intruder, but one that he would happily tolerate for the sake of his brother.